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Hunter selection and long-term trend (1881-2008) of red deer trophy sizes in Hungary
Abstract
1. Human harvesting has a large impact on natural populations and may cause undesirable life-history changes. In wild ungulate populations, unrestricted trophy hunting may cause strong selection pressures resulting in evolutionary change towards smaller trophies. It has rarely been tested how harvesting selection varies in space and time, and whether directional hunter selection is sufficiently strong to induce long-term decreases in trophy size in century- scale data.
2. We analysed two unique data sets of harvesting records spanning decade (1973–2008) and century scales (1881–2008) to identify changes in trophy size and how harvesting selection varies in space and time in red deer Cervus elaphus. We contrasted predictions from the trophy-hunting depletion, the restricted trophy hunting and the hunting pressure hypotheses. 3. Foreign hunters selected older and larger males than local hunters, but selection patterns for age-specific trophy size between counties and over time were dynamic. Patterns of red deer trophy size development from exhibitions (representing the ‘upper tail’ of antler sizes) were remarkably similar across Hungary from 1881 to 2008. A weak decline in trophy size between 1881 and 1958 was followed by a strong increase in trophy size between 1958 and 1974, culminating in a period of stable antler tine numbers and a weak decline in beam length until 2008.
4. We rejected the trophy hunting depletion hypothesis due to the increase in trophy size after a period of decline; patterns were most consistent with the hunting pressure hypothe- sis. Large increases in trophy size during 1958–1974 were likely due to a relief in hunting pressure due to implementation of strict management regulations allowing stags to grow old after the massive overharvesting during World War II, but we cannot exclude impacts from environmental factors, and that data from trophy exhibitions may underestimate trends.
5. Synthesis and applications. Trophy hunting does not necessarily lead to a non-reversible decline in trophy size, even over century-long time-scales. To ensure sustainable trophy hunting management, we need to consider factors such as spatial and temporal refuges, compensatory culling, saving stags until prime-age culmination and higher prices for larger trophies.
... Najefektívnejšu formu zhodnotenia produkcie poľovných pozemkov predstavuje organizovanie poľovníckej turistiky a poplatkového lovu (Lehocký & Kuric 2007, Rivrud et al. 2013. Poplatkový lov je popri organizačných poplatkoch (Anonymus 2017(Anonymus , 2018a(Anonymus , b, 2019a zameraný aj na kvalitatívne zhodnotenie chovu úlovkami. ...
... No doplnkové kŕmenie je možné použiť aj na zlepšenie zimného prežitia (Doenier et al. 1997) a zvýšenie reprodukčného úspechu zvierat (Robb et al. 2008). Na druhej strane okrem rozdielov v biotopoch zohráva pri formovaní potravy jeleňov dôležitú úlohu riziko predácie (Churski et al. 2020 Rivrud et al. 2013). PETV medzi obdobiami stúpa a najvýraznejšie sa na tom podieľa u oboch hodnotených oblasti jelene. ...
... No boli aj PR s vyšším zastúpením medailových jedincov, no s nižším počtom (prípadne bez) zlatých trofejí. Tieto nižšie hodnoty v zastúpení zlatých trofejí môžu súvisieť s nízkym vekom lovených jedincov, ktorý bol vyhodnotený v rámci územia(Štofík et al. 2019) a je výrazne nižší, ako by mal byť k zabezpečeniu kvalitnejších medailových trofejí (napr.Lehocký & Kuric 2007, Rivrud et al. 2013. Tu môže zohrávať dôležitú úlohu kvalitný genofond jelenov(Paule & Krišta 1984), čo viedlo v minulosti k vyhláseniu Poľany za oblasť so zvláštnou pozornosťou -chránenú poľovnú oblasť(Kaštier et al. 2013). ...
Trophy quality in hunted ungulates in northeastern Slovakia (Cetartiodactyla). Based on the data from trophy hunting statistics (1997–2019), this paper describes changes in the potential economic trophy value evaluation of hunted ungulates (PETV) by comparison of two groups of areas, (1) the hunting grounds with wolf protection (since 2014), and (2) the hunting grounds without wolf protection. In both groups of areas in the long-term aspect (1997–2019), the value of PETV had an increasing trend in the roe deer, wild boar, and red deer. Since 2014, in the areas with wolf protection the average value of PETV was at the level of 249 €/year/km2 (SD 69 €/year/km2) and in the areas without wolf protection, it was 185 €/year/km2 (SD 8 €/year/km2). Since 2014, in the areas with wolf protection, the mortality did not affect the PETV trend, but in the red deer a significant fluctuation in PETV values was observed compared to the previous period. Since 2014, in the areas with wolf protection, a qualitative increase in the value of hunted red deer trophies was registered, in almost all C.I.C. categories above 170 points.
... Variation in harvest selectivity has been studied in cervids by comparing hunting methods (Martinez et al. 2005) or resident and nonresident hunters (Mysterud et al. 2006, Schmidt et al. 2007, Rivrud et al. 2013. For example, in Alaska, USA, guided hunters harvested moose (Alces alces) with larger antlers compared to non-guided hunters because guides had a better knowledge of low-density areas producing large-antlered moose (Schmidt et al. 2007). ...
... Refugia from hunting such as the Spatsizi wilderness park in the low hunting area could also counter artificial selection by providing a source of non-selected immigrants (Tenhumberg et al. 2004, but see Pelletier et al. 2014). A recent study in Hungary reported no long-term negative trend in red deer antler size despite more than a century of trophy hunting (Rivrud et al. 2013). Unlike horns, however, antlers are regrown each year and are strongly influenced by interannual variation in environmental conditions (Schmidt et al. 2001, Kruuk et al. 2002. ...
... Development of horns and antlers is affected by factors influencing food quantity or quality, such as population density and climate (Jorgenson et al. 1998, Schmidt et al. 2001, Festa-Bianchet et al. 2004, Mysterud et al. 2005. We controlled for climate, but unfortunately, no reliable measure of density was available, a problem often encountered in studies examining the effects of trophy hunting at large spatial scales (e.g., Rivrud et al. 2013). Local wildlife managers' opinions and aerial counts conducted every 3 or 4 years between 1987 and 2011, however, suggest that density of Stone's sheep was relatively stable over time in both regions Hartwig 2004, Kuzyk et al. 2014). ...
Selective harvest may lead to rapid evolutionary change. For large herbivores, trophy hunting removes males with large horns. That artificial selection, operating in opposition to sexual selection, can lead to undesirable consequences for management and conservation. There have been no comparisons of long-term changes in trophy size under contrasting harvest pressures. We analyzed horn measurements of Stone's rams (Ovis dalli stonei) harvested over 37 years in two large regions of British Columbia, Canada, with marked differences in hunting pressure to identify when selective hunting may cause a long-term decrease in horn growth. Under strong selective harvest, horn growth early in life and the number of males harvested declined by 12% and 45%, respectively, over the study period. Horn shape also changed over time: horn length became shorter for a given base circumference, likely because horn base is not a direct target of hunter selection. In contrast, under relatively lower hunting pressure, there were no detectable temporal trends in early horn growth, number of males harvested, or horn length relative to base circumference. Trophy hunting is an important recreational activity and can generate substantial revenues for conservation. By providing a reproductive advantage to males with smaller horns and reducing the availability of desirable trophies, however, excessive harvest may have the undesirable long-term consequences of reducing both the harvest and the horn size of rams. These consequences can be avoided by limiting offtake.
... Variation in harvest selectivity has been studied in cervids by comparing hunting methods (Martinez et al. 2005) or resident and nonresident hunters (Mysterud et al. 2006, Schmidt et al. 2007, Rivrud et al. 2013. For example, in Alaska, USA, guided hunters harvested moose (Alces alces) with larger antlers compared to non-guided hunters because guides had a better knowledge of low-density areas producing large-antlered moose (Schmidt et al. 2007). ...
... Refugia from hunting such as the Spatsizi wilderness park in the low hunting area could also counter artificial selection by providing a source of non-selected immigrants (Tenhumberg et al. 2004, but see Pelletier et al. 2014). A recent study in Hungary reported no long-term negative trend in red deer antler size despite more than a century of trophy hunting (Rivrud et al. 2013). Unlike horns, however, antlers are regrown each year and are strongly influenced by interannual variation in environmental conditions (Schmidt et al. 2001, Kruuk et al. 2002. ...
... Development of horns and antlers is affected by factors influencing food quantity or quality, such as population density and climate (Jorgenson et al. 1998, Schmidt et al. 2001, Festa-Bianchet et al. 2004, Mysterud et al. 2005. We controlled for climate, but unfortunately, no reliable measure of density was available, a problem often encountered in studies examining the effects of trophy hunting at large spatial scales (e.g., Rivrud et al. 2013). Local wildlife managers' opinions and aerial counts conducted every 3 or 4 years between 1987 and 2011, however, suggest that density of Stone's sheep was relatively stable over time in both regions Hartwig 2004, Kuzyk et al. 2014). ...
Selective harvest may lead to rapid evolutionary change. For large herbivores, trophy hunting removes males with large horns. That artificial selection, operating in opposition to sexual selection, can lead to undesirable consequences for management and conservation. There have been no comparisons of long-term changes in trophy size under contrasting harvest pressures. We analyzed horn measurements of Stone's rams (Ovis dalli stonei) harvested over 37 years in two large regions of British Columbia, Canada, with marked differences in hunting pressure to identify when selective hunting may cause a long-term decrease in horn growth. Under strong selective harvest, horn growth early in life and the number of males harvested declined by 12% and 45%, respectively, over the study period. Horn shape also changed over time: horn length became shorter for a given base circumference, likely because horn base is not a direct target of hunter selection. In contrast, under relatively lower hunting pressure, there were no detectable temporal trends in early horn growth, number of males harvested, or horn length relative to base circumference. Trophy hunting is an important recreational activity and can generate substantial revenues for conservation. By providing a reproductive advantage to males with smaller horns and reducing the availability of desirable trophies, however, excessive harvest may have the undesirable long-term consequences of reducing both the harvest and the horn size of rams. These consequences can be avoided by limiting offtake.
... Harvesting of big game populations can impose strong pressures on natural populations, and may cause undesirable life history changes over shorter periods of time than expected from natural selection (Coltman et al. 2003; Garel et al. 2007). The impacts of trophy hunting remains uncertain, as the current studies mostly provide data over fairly short time spans, have low sample sizes and are not replicated time series (Rivrud et al., 2013). As data from long-term monitoring are rare and hard to obtain in harvested populations, patterns of harvesting selection in ungulates have been studied by comparing hunting methods (Martinez et al. 2005; Torres-Porras et al. 2009) or categories of hunters by comparing local hunters vs. foreign trophy hunters (). ...
... Age is estimated by tooth wear (Szidnai 1978), a method known to show some variation for older individuals (Mysterud and Østbye 2006) but also variation between (Veiberg et al. 2007) and within populations (Nussey et al. 2007). However, since the same method is utilized over the full data set, it is unlikely that over-or underestimation of age play a role for the observed patterns, but we are aware that the ageing method probably adds some confusion to the data, particularly for older individuals (Rivrud et al., 2013). from these data, age distribution of harvested stags, weight distribution of antlers and the average antler weights of each age class can be calculated. ...
... As a consequence that the overall mortality increased during the first 9 years of life, the proportion of mortality during the old age declined from 20% to 5% (Figure 4).Table 2. Number of males dying according to age in cohorts born between 1983 and 2001, Somogy county (cells yellow shaded same as inTable 1) These kinds of changes cannot be analysed without a database like ours. It allows to study details that are not available at a given point of time and that can only be accumulated on several decades time scales (Rivrud et al., 2013). 1982 1984 1986 1988 1990 1992 1994 1996 1998 1984 1986 1988 1990 1992 1994 1996 1998 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 ...
Wildlife management should be based on data and management decisions which require adequate information. In case of red deer population sizes, the level of hunting pressure, and the effects of harvesting on the male population are debated in many form. Several relationships and effects of management and hunting cannot be well understood without the collection and use of long- term data. Since 1970 it is compulsory in Hungary to present antlers of harvested red deer for a trophy evaluation (scoring) by Trophy Scoring Committees authorized by the state authorities. This paper presents some of the uses of trophy scoring data on the basis of Somogy county. Population reconstruction, comparison of mortality patterns of different cohorts, and spatio-temporal differences in age composition of shot males are discussed.
... This scoring system, however, relies heavily on quantitative characters, antler weight being weighed by 22% among the variables used in the calculation. Oscillations in Figure 8a are largely consonant with the predicted patterns in the number of antler tines and beam length of 2926 antlers shown in exhibitions during 1881-2008 [48]. Consequently, when only antler weight itself is plotted against the year of the kill a higher, moderate correlation can be detected, confirming a substantial diachronic increase in the largest record antlers during the 45 years interval studied (Figure 8b). ...
... Building on the information on world record CIC scores used in 1999 [44], the updated 2005 list was consulted, thus 85 additional cases were included in Figure 8a [46,47]. A more detailed analysis of data on these trophies displayed a weak decline in size between 1881 and 1958 in Hungary, followed by an increase in trophy size between 1958 and 1974 (detected in my previous analysis if CIC scores [44]), culminating in a period of stable antler tine numbers and a weak decline in beam length until 2008 [48]. This stagnation after 1990 is also visible in Figure 8. ...
A stray find of red deer antler from Sweden with the braincase was collected due to an apparently pathological deformation, the strongly retarded right antler. Measurements of the complete left antler inspired the analysis of general antler conformation in order to place this archaeological specimen in a zoological context. This stray find and another prehistoric antler from Sweden as well as three complete prehistoric antlers from Hungary were metrically compared using measurements of over 17,000 trophies of extant red deer from Hungary. The results confirmed that the stray specimen from Sweden and prehistoric antlers from Hungary were similar in that they were stouter (smaller length measurements but greater circumferences) than their 20th century counterparts. Most of their measurements fell within the ±1 standard deviation interval of the means of extant trophies. The pathological lesion on the studied stray specimen directed attention to the role of human selection. Twentieth century record trophies show a significant increase in antler weight and “quality” as defined in the international trophy grading system. While these morphometric observations cannot be taken as a proxy for absolute dating or precise contextual identification for the stray find central to this study, its size and apparent lack of consistent human selection (pathological deformation, “archaic” antler proportions) point to possibly early origins, prior to major human influence.
... Therefore, the evidence for or against harvest-induced microevolutionary change is limited. Rivrud et al. (2013) found no long-term decreases in antler size of red deer in Hungary. Management of red deer in Hungary, and in central Europe in general, does not strongly select against large-antlered males and includes culling of males with small antlers, which could compensate for a possible evolutionary effect of trophy hunting (Mysterud and Bischof 2010). ...
... When entries in these books are based on a minimum "score," however, they report a truncated distribution and are less likely to detect decreases . Trophy shows, such as those typical of central Europe, may be more useful if they report the entire harvest or the "largest" animals shot in any 1 year, so they would reflect temporal changes in the upper tail of the distribution of weapon size (Rivrud et al. 2013). ...
Intense selective harvest of large mammals who carry the largest weapons may lead to an evolutionary shrinkage of those weapons. Currently, evidence suggesting evolutionary effects of harvest is limited to a few species of Bovidae and only 1 study has obtained data indicating a genetic effect. To have an evolutionary impact, harvest must be intense, persistent over time, similar over a large area without an effective source of unselected immigrants, and remove large individuals before they have a chance to breed. Many current harvest schemes do not fulfill all of these requirements, and they are unlikely to cause evolution. Before changes in weapon size over time are attributed to evolution, potential environmental sources of change, mainly density and climate, must be considered. We suggest that the role of weapon size in determining reproductive success, especially in interaction with male age, will determine whether or not intensive selective harvests may have evolutionary consequences. Age at harvest is a very important variable to consider. Changes in age structure over time may reveal underlying changes in harvest pressure or selectivity. A lack of data hampers our ability to assess the potential evolutionary effects of selective hunting. We provide a list of research hypotheses required to advance our ability to assess the evolutionary sustainability of current management practices.
... Unlimited trophy hunting exerts a pressure on the populations of game species, tending to act towards a decrease of trophy size. As a result, changes in such morphometric parameters could reflect changes in the local system of hunt management (Rivrud et al. 2013). One of the most expressive examples of this is the reduction in horn size in the rams of bighorn sheep (Ovis canadensis), caused by the simultaneous effects of environmental factors and selective hunting based on best trophies (Coltman et al. 2003, Garel et al. 2007, Allendorf & Hard 2009, Hedrick 2011. ...
... Our analysis proved that differences in antler parameters are significant between the countries with different hunting strategies, and that the biggest trophies are in Lithuania, where compensatory hunting is implemented legally. Selection is conducted by hunting out roe deer bucks characterized by insufficient quality (abnormal antler shape, low body weight (Lockow 1991, Drechsler 1992) and by limiting trophy hunting (Rivrud et al. 2013). In Lithuania, good quality roe deer bucks may be hunted only if they are at least 5 years of age and have an antler weight of no less than 300-320 g (Baleišis et al. 2003). ...
With antlers valuated as trophies, ungulates experience high pressures due to selective hunting. The response of the population differs depending on the type of hunting strategy used, and trophies serve as a suitable proxy to answer this question. For example, unrestricted trophy or leisure hunting results in a diminishing quality of trophies. We evaluated the effect of the applied hunting strategy on European roe deer (Capreolus capreolus) antler size in Lithuania, Latvia and Estonia between 2006 and 2011. With the aim of preserving good quality bucks up to 5 years of age, compensatory hunting (culling) is obligatory in Lithuania. To the north, in the other two Baltic countries, roe deer buck are hunted with no age limit. Based on nonparametric tests and forward stepwise discriminant function analysis of antler morphometric characters, Lithuanian roe deer antlers were found to be significantly larger (about 40 % by mean weight and volume for the 35 biggest trophies). We conclude that bucks in Latvia and Estonia are hunted out before they reach trophy maturity (5-7 years). The antlers of fast growing bucks in the age of 3-4 years are almost as big, so they are untimely eliminated from the population. We recommend extending the preservation period of healthy roe deer buck to 6 years of age, giving hunters the possibility to estimate their age not solely on antler size, but also on other body characters.
... Many studies investigating the effects of weather and climate on growth of horns or antlers used data from harvested animals ( Table 1, Mysterud et al. 2005, Rivrud et al. 2013). The advantages of using harvest data often include a very large sample size and wide geographical coverage (Büntgen et al. 2014, Rivrud et al. 2013 Accepted Ar ticle 'This article is protected by copyright. ...
... Many studies investigating the effects of weather and climate on growth of horns or antlers used data from harvested animals ( Table 1, Mysterud et al. 2005, Rivrud et al. 2013). The advantages of using harvest data often include a very large sample size and wide geographical coverage (Büntgen et al. 2014, Rivrud et al. 2013 Accepted Ar ticle 'This article is protected by copyright. All rights reserved.' ...
The development of male secondary sexual characters such as antlers or horns has substantial biological and socio-economic importance because in many species these traits affect male fitness positively through sexual selection and negatively through trophy hunting. Both environmental conditions and selective hunting can affect horn growth but their relative importance remains unexplored. We first examined how a large-scale climate index, the Pacific Decadal Oscillation (PDO), local weather and population density influenced both absolute and relative annual horn growth from birth to three years of male bighorn sheep Ovis canadensis over 42 years. We then examined the relative influence of environmental conditions and evolution mainly driven by trophy hunting on male horn length at three years of age. Horn growth was positively influenced by low population density and warm spring temperature, suggesting that ongoing climate change should lead to larger horns. Seasonal values of PDO were highly correlated. Horn growth increased with PDO in spring or summer at low density, but was weak at high density regardless of PDO. The interaction between population density and PDO in spring or summer accounted for a similar proportion of the observed annual variation in horn growth (32% or 37%) as did the additive effects of spring temperature and density (34%). When environmental conditions deteriorated, males allocated relatively more resources to summer mass gain than to horn growth, suggesting a conservative strategy favoring maintenance of condition over allocation to secondary sexual characters. Population density explained 27% of the variation in horn length, while evolutionary effects explained 9% of the variance. Thus, our study underlines the importance of both evolution and phenotypic plasticity on the development of a secondary sexual trait. This article is protected by copyright. All rights reserved.
... We concluded that: (1) the effect of trophy hunting on size of horn or tusk size and age at harvest is species specific as it does not necessarily affect trophy size and the age at harvest of harvested herbivores, (2) quota size allocation may not reflect the trophy size and offtake levels over the time, and (3) political and economic performance may not necessarily affect the harvesting regime patterns though external influences though moratoriums may possibly reduce the offtake levels over time. Accordingly, trophy hunting may not necessarily lead to irreversible trophy size over time but requires systematic monitoring and sound management interventions for sustainability [101]. ...
... We recommend that conservationists and protected area managers may consider to: (1) emphasise the need for ecological principles in the quota setting process and in some cases reduce or temporarily stopping hunting (i.e., introducing fallow or resting hunting years on a rotational basis) of some species, (2) create temporal and spatial refuges to facilitate 'trophy hunting rest' for some species promote reproductive to the desirable phenotypic sizes such as trophy size [102], (3) introduce and firmly implement age based harvesting policies across all trophy hunted species instead of lions only, through enforcing penalties for harvesting below threshold age individuals [46,89], and (4) introduce a variable trophy fee pricing system based on trophy size where the fees are determined on the trophy size [71,101]. These measures could then be replicated at micro-scale and national level in other areas where trophy hunting is being practiced to ensure sustainability. ...
The selective nature of trophy hunting may cause changes in desirable phenotypic traits in harvested species. A decline in trophy size of preferred species may reduce hunting destination competitiveness thus compromising the sustainability of trophy hunting as a conservation tool. We explored the trophy quality and trends in harvesting patterns (i.e., 2004–2015) of Cape buffalo (Syncerus caffer), African elephant (Loxodonta africana), greater kudu (Tragelaphus strepsiceros) and sable (Hippotragus niger) in Matetsi Safari Area, northwest Zimbabwe. We used long-term data on horn and tusk size, age, quota size allocation and offtake levels of selected species. To analyse the effect of year, area and age on the trophy size, quota size and offtake levels, we used linear mixed models. One sample t-test was used to compare observed trophy size with Safari Club International (SCI) minimum score. Trophy sizes for Cape buffalo and African elephant were below the SCI minimum score. Greater kudu trophy sizes were within the minimum score threshold whereas sable trophy sizes were above the SCI minimum score between 2004 and 2015. Age at harvest for Cape buffalo, kudu and sable increased whilst that of elephant remained constant between 2004 and 2015. Quota size allocated for buffalo and the corresponding offtake levels declined over time. Offtake levels of African elephant and Greater kudu declined whilst the quota size did not change between 2004 and 2015. The quota size for sable increased whilst the offtake levels fluctuated without changing for the period 2004–2015. The trophy size and harvesting patterns in these species pose a conservation and management dilemma on the sustainability of trophy hunting in this area. We recommend: (1) temporal and spatial rotational resting of hunting areas to create refuge to improve trophy quality and maintenance of genetic diversity, and (2) introduction of variable trophy fee pricing system based on trophy size.
... The size of red deer antlers, however, is highly dependent upon yearly environmental conditions, which may override the substantial genetic component of antler size (Kruuk et al. 2014). In addition, trophy red deer stags are often harvested at or after their peak breeding age (Rivrud et al. 2013), unlike bighorn sheep where the largest-horned males are shot before they become dominant rams. There may be a fundamental difference in susceptibility to hunter-induced evolution between cervids (and antilocaprids) and bovids (and pachyderms). ...
... Trophy record books based on a very high minimum 'score' are nearly useless to monitor horn, tusk or antler size (Festa-Bianchet et al. 2015). Trophy shows that record 'the biggest each year' may not be quite as biased (Rivrud et al. 2013). Data on annual horn increments in bovids can help considerably in overcoming these biases and provide useful information for assessing the selective impacts of trophy hunting. ...
Potential evolutionary consequences of selective hunting of mammals are controversial because of limited evidence and important socio-economic impacts. Several ecological and management variables facilitate evolutionary responses to selection for horn, tusk or antler size, including strong selective hunting pressure; harvest of males with large horns, tusks or antlers before they can breed; unavailable or ineffective sources of unselected immigrants; and age-dependent relationships between horn, tusk or antler size and male mating success. Plastic responses of male horns, tusks and antlers to environment are probably more common than evolutionary changes. Evidence for evolutionary effects of selective hunting is strong for large mammals where biological characteristics and hunting regulations combine to favour them.
... Recent publications have examined an alternative to these short time series by analyzing entries in the Boone and Crockett record book (Monteith et al. 2013), other record books (Nuzzo and Traill 2014), or trophy shows (Rivrud et al. 2013), that span over a century. Record books and trophy shows, however, provide truncated samples because only large trophies are included, and may not detect declines over time. ...
... Analyses of record-book entries offer insights into what hunting trophies are listed but cannot assess whether or not selective hunting leads to artificial selection. The bias involved in analyses of trophy shows (Rivrud et al. 2013) is unclear, because the criteria for inclusion are not specified, and may be affected over time by hunters' perception of what constitutes a large trophy, leading to a problem of shifting baselines similar to that encountered in fisheries and in other fields of conservation biology (Papworth et al. 2009). We used a realistic but high cutoff for inclusion in our simulated record book, corresponding to the top 5% of horn lengths of an unhunted population. ...
Many agencies and researchers use data from harvested animals to study temporal trends in phenotype. For large mammals, complete harvest records are typically only available for the past few decades, but records of the largest trophies have been collected for over a century. To examine whether record books and data from male bighorn sheep (Ovis canadensis) harvested under a minimum-curl regulation could detect temporal trends in horn length, we simulated populations of trophy-harvested male bighorn sheep where horn length was modeled to increase, remain stable, and decrease over time. All populations experienced a simulated harvest based on a minimum horn length, but only horns in the longest 5% of the initial distribution were entered in a fictional record book. We then assessed whether monitoring of harvested and “record” males detected temporal trends. Data from selective harvest underestimated declines and initially underestimated increases, but qualitatively detected both trends. Record-book entries, however, severely underestimated increases and did not detect declines, suggesting that they should not be used to monitor population trends. When these biases are taken into account, complete trophy harvest records can provide useful biological information.
... Big game (ungulate) management was focused on red deer, and ungulates were available only for a limited number of hunters. Trophies of ungulates received great recognition and a protective hunting culture determined their management (Csányi and Lehoczki, 2010;Rivrud et al., 2013); big game shooting was a rather privileged activity and restricted to a few Hungarian and paying foreign hunters (Csányi and Lehoczki, 2010). However, as populations of small game have declined and ungulate populations have increased, management of and attitudes towards the hunting of these species has been altered signifi cantly. ...
... • In 2012, the income originating from the payments of the domestic hunters showed a weak correlation with the density of ungulates per km 2 (r 2 = 0.289). This may be in as a result of the fact that paying domestic hunters are normally shooting younger, smaller trophy males or female and young ungulates (Rivrud et al., 2013). • A very strong correlation was found between the income from the shot game sold (carcass and meat) and the density of ungulates harvested per km 2 (r 2 = 0.868). ...
... antlers, lower jawbone, hind-legs, uterus, femur bone marrow; e.g. Hewison et al. 1996;Sand and Cederlund 1996;Azorit et al. 2003;Zannèse et al. 2006;Martin et al. 2013;Rivrud et al. 2013;Becciolini et al. 2016;Cook et al. 2021a, b). For large, long-lived terrestrial herbivores, body mass is strongly related to both survival, reproduction, and, ultimately, population dynamics (e.g. ...
Hunter-collected data and samples are used as indices of population performance, and monitoring programs often take advantage of such data as ecological indicators. Here, we establish the relationships between measures of skeleton size (lower jawbone length and hind-leg length) and autumn carcass mass of slaughtered individuals of known age and sex of the high Arctic and endemic Svalbard reindeer (Rangifer tarandus platyrhynchus). We assess these relationships using a long-term monitoring dataset derived from hunted or culled reindeer. The two skeleton measures were generally strongly correlated within age class. Both jaw length (R² = 0.78) and hind-leg length (R² = 0.74) represented good proxies of carcass mass. These relationships were primarily due to an age effect (i.e. due to growth) as the skeleton measures reached an asymptotic size at 4–6 years of age. Accordingly, strong positive correlations between skeleton measures and carcass mass were mainly evident at the young age classes (range r [0.45–0.84] for calves and yearlings). For the adults, these relationships weakened due to skeletal growth ceasing in mature animals causing increased variance in mass with age—potentially due to the expected substantial impacts of annual environmental fluctuations. As proxies for carcass mass, skeleton measurements should therefore be limited to young individuals. Although body mass is the ‘gold standard’ in monitoring large herbivores, our results indicate that skeleton measures collected by hunters only provide similar valuable information for young age classes, particularly calves and yearlings. In sum, jaw length and hind-leg length function as proxies identical to body mass when documenting the impacts of changing environmental conditions on important state variables for reindeer and other herbivores inhabiting highly variable environments.
... The red deer (Cervus elaphus L. 1758) is one of the most widespread and valuable European game species (Ludt et al. 2004;Milner et al. 2006). Consequently, its populations have been extensively managed, introduced, restocked, and selectively hunted for centuries or even millennia (Martínez et al. 2002;Haanes et al. 2010;Carden et al. 2012;Rivrud et al. 2013;Queirós et al. 2014;Hoffmann et al. 2016;Stanton et al. 2016;Frantz et al. 2017;Galarza et al. 2017). Furthermore, during the last decades, the keeping of deer in enclosures has spread all over the world, and the species is farmed for venison and antler products (Milner et al. 2006;Wada et al. 2010;Zachos and Hartl 2011;Bana et al. 2018). ...
After the last glacial, the Carpathian Basin was repopulated from either eastward or northward colonisation routes for various species; one of these was the emblematic member of the European megafauna, the red deer, Cervus elaphus. We analysed 303 red deer individuals from the middle of the region, in seven Hungarian game reserves, at ten microsatellite loci (C01, C229, T26, T108, T123, T156, T172, T193, T501, T507), to investigate the genetic diversity of these subpopulations. We discovered high levels of genetic diversity of red deer subpopulations; allelic richness values ranging 4.99-7.01, observed heterozygosity 0.729-0.800, polymorphic information content 0.722-0.806, and Shannon's information index 1.668-2.064. Multi-locus analyses indicated population admixtures of various degrees that corresponded to geographical location, and complex genetic structures were shown by clustering. Populations in the southwestern and the northeastern parts of the region formed two highly separated groups, and the red deer from populations in between them were highly admixed (in western Pannonia/Transdanubia, where the Danube flows into the Carpathian Basin). This pattern corresponds to the distribution of mitochondrial as well as Y-chromosome lineages. Assignment tests showed that a large fraction of individuals (29.4%) are found outside of their population of origin, indicating that the dispersal of red deer is rather common, which could be expected considering the life course of the species.
... In a broader array of cases, human interaction with wild animals blurs the line with the commensal and prey pathways for domestication, with human-induced selection often yielding harmful changes for populations. Animals of recreational value, like hunting or sport fishing, are often bred and harvested selectively (Fig. 1) due to specific phenotypic characteristics that make them especially desirable to hunters such as large antlers (Double Dime Whitetails 2021) or body size, in addition to preferred behaviors like reduced movement rates (Rivrud et al. 2013;Festa-Bianchet 2017;Leclerc et al. 2019). This "unnatural selection" resulting from HIREC-adjacent living and selection in managed populations has the potential to negatively affect genetic diversity and fitness (Allendorf and Hard 2009). ...
With nearly all life on earth experiencing direct or indirect effects of human activity, there is an urgent need to understand how organisms do or do not adapt to human-induced environmental change. Domestication was an early crash into the Anthropocene for some species, and the response of animal populations to domestication selection gives us insights on how plastic responses and evolutionary changes interact to determine the fate of wild vertebrates responding to a human-altered world. We consider intentional breeding, managed hunting, and extermination as part of a continuum of anthropogenic agents of ecological selection and highlight shared targets of selection between domestication and human-induced selection pressures more broadly. Many of the traits that predict successful domestication also predict adaptation of wild animals to human-dominated environments. Domestic animals are also a source for feral lineages and for genetic exchange with wild populations. Shared ecological constraints and gene flow thus contribute to convergent or congruent changes across a spectrum of responses to human influence. Evaluating domestication as another source of anthropogenic selection yields insights for conservation and a promising way to understand mechanisms of behavioral adaptation.
Significance statement
In this review, we draw insights for conservation from domestication—the oldest and most intense evolutionary interaction between animals and humans. Domestication is a special case of organisms successfully responding to an abrupt shift towards human-altered environments, and success in those environments depends on the same factors that make some animals easier to domesticate than others. Domestication has the potential to simultaneously inform us how behavior and genetics contribute to the process of human adaptation in animals and provide a window into the processes required for animals to become human-adjacent. Understanding how animals adapt in our presence yields clues as to how contemporary species react to decreasing habitat and increasing contact with humans.
... There are sweat, sebaceous, preorbital, and interdigital glands. There are two molts per year -in spring and at the end of summer [37][38][39][40]. ...
The article deals with the analysis of risks of an investment project on the example of a project for breeding red deer in the Samara region. The purpose of the study is to determine the list and degree of risks of an investment project associated with the breeding of red deer in the Samara region. Tasks to be solved: - study of the features of the red deer as an investment object; - preparation of a feasibility study for an investment project for breeding red deer, taking into account the climatic, natural, economic and legal characteristics of the region; - determination of the qualitative and quantitative parameters of the risks of an investment project being implemented under these conditions. An investment project related to the breeding of red deer in the Samara region has a unique set of investment risks. A standard qualitative and quantitative methods for assessing the risks and sustainability of investment projects can be used to determine the structure and size. Under these conditions, the investment project has a low and medium level of investment risks, mainly due to the uniqueness of the manufactured product and significant budgetary support for the project. When determining a quantitative risk assessment, it can be seen that when the most significant parameters of the project change in the range from -20% to + 20%, its results remain positive, and the planned production volumes are significantly higher than the break-even point and exceed it by more than 10 times.
... For bighorn sheep in Alberta, there is a lack of data on spatiotemporally explicit demographic and dispersal rates of protected and exploited populations. Despite their biases (Pelletier et al. 2012;Festa-Bianchet et al. 2014), records of harvested animals are an alternative source of information as they provide a wide geographical and temporal coverage (Rivrud et al. 2013;Büntgen et al. 2014;Douhard et al. 2016). Our findings from harvest data not only confirm that current hunting regulations select against large horn size Poisson et al. 2020) but also underline how harvest pressure can affect evolutionary consequences. ...
Trophy hunting can affect weapon size of wild animals through both demographic and evolutionary changes. In bighorn sheep (Ovis canadensis Shaw, 1804), intense harvest of young males with fast-growing horns may have partly driven long-term decreases in horn size. These selective effects could be dampened if migrants from protected areas, not subject to artificial selection, survived and reproduced within hunted populations. Bighorn rams undertake long-distance breeding migrations in the weeks preceding the late-November rut. We analysed records of >7 800 trophy bighorn rams shot from 1974 to 2019 in Alberta, Canada, to test the hypothesis that high harvest pressure during breeding migrations was correlated with a greater decrease in horn size. We compared areas with and without a pronounced harvest peak in late October, when male breeding migrations begin. Areas without a pronounced harvest peak in late October, that likely experienced a lower harvest rate, showed a similar temporal decline in horn size, but no increase in age at harvest suggesting a possibly weaker decline in horn growth. Our study suggests that unselected immigrants from protected areas could partly buffer the effects of intense trophy hunting only if harvest pressure was reduced when breeding migrations commence.
... Such studies are relatively common for game species in other parts of the world (e.g. Europe; Rivrud et al. 2013), but are lacking in Australia. ...
Context Little is known about wildlife harvesting by licensed recreational hunters in Australia, where both native and introduced species are hunted. It is important to understand harvest trends to assess sustainability for native species and implications for population control of introduced species. Aim The aim of this study was to analyse trends in hunter participation, activity and efficiency, and wildlife harvest, including effects of climate, in Victoria, Australia, for three game species groups: introduced deer, native waterfowl (ducks) and one native grassland species, stubble quail (Coturnix pectoralis). Methods Telephone surveys of a random sample of licenced Victorian hunters were performed annually from 2009 to 2019. Hunters were asked to quantify their hunting effort and the number of animals harvested. The respondents’ answers were analysed to estimate measures of hunter success, activity and efficiency. Bayesian modelling was applied to these data, accounting for changes over time, differences between survey periods for all licence types, and random effects for over-dispersion. The effect of climate on game bird hunter activity and harvest was estimated, as measured by the El Niño-Southern Oscillation (ENSO). Results Over 11 years, annual deer harvest (all species) increased exponentially, at a mean annual rate of 17% (95% credible interval: 14–21%), and the number of deer hunters increased at 8% (5–11%). In contrast, for ducks and stubble quail, hunter numbers remained relatively unchanged, with no evidence of consistent change to total harvests over time, unrelated to changes in environmental conditions or regulations. The annual duck harvest was influenced by ENSO and hunting regulations. The annual stubble quail harvest exhibited ‘boom-and-bust’ dynamics, with an exceptionally large harvest immediately after a La Niña season. Conclusions Long-term monitoring of harvest trends in south-eastern Australia revealed stark differences between introduced deer and native birds: harvest of deer increased rapidly whereas equivalent rates for game birds were either stable or declining. Seasonal effects had a strong influence on game bird harvest. Environmental and regulatory conditions were influential for harvest outcomes for ducks and stubble quail. Implications This study filled a key knowledge gap around managing harvesting of game species, but increased scrutiny is warranted in this field.
... There are also additional causes of temporal trends in lifehistory traits, such as the selective harvest of mammals (e.g. trophy hunting for large horns or antlers decreases horn or antler size : Pigeon et al., 2016;Rivrud et al., 2013). Understanding how these anthropogenic effects temporally modify geographic clines is important for the management of wild organisms and to maintain their original lifehistory traits in the Anthropocene. ...
Geographic clines in life‐history traits are often recognized as adaptations to the associated transitional environments. As life‐history traits evolve in response to anthropogenic processes, these geographic clines can change over time.
The geographic and temporal trends of reproductive traits in Japanese chum salmon Oncorhynchus keta were analysed. Data were collected from 23 rivers located between 36° and 45° north latitude and 136° and 146° east longitude from 1994 to 2010.
We confirmed the geographic clines of reproductive traits: relative gonad weight increased in more northeasterly locations, and females had fewer, but larger, eggs in more northeasterly locations after standardization by body size.
The geographic clines changed over the years. The northeastward geographic trend of increasing gonad weight became more pronounced over time. Temporal trends towards smaller but more numerous eggs were evident, especially in northeasterly locations.
Under natural and sexual selection, gonadal investment should be constrained by the energetic demands of the cost of migration, particularly in southwesterly locations (which are farthest from the feeding grounds), and by breeding competition during natural reproduction. In addition, females should have fewer but larger eggs owing to a constraint on growth opportunities for their offspring in more northeasterly regions of Japan, which are colder and have less available food. However, global warming may mitigate this constraint on growth opportunities in northeastern Japan by increasing river water temperatures. Moreover, we consider that relaxation of the effects of natural and sexual selection on intense breeding competition and early growth conditions has occurred through domestication selection by hatchery programmes. These may have caused temporal shifts in geographic clines.
We should consider several co‐occurring anthropogenic impacts on natural and sexual selection when evaluating the life‐history traits of organisms. For the sustainable use of biological resources, maintaining geographically adapted life‐history traits during adaptation to climate change is essential. Therefore, the conservation of wild salmon populations formed by natural selection is preferable to the stocking of hatchery‐reared fry.
... Although trophy hunting rarely influences population size, population structure may be altered by the disproportionate removal of animals relative to age or sex (Milner et al. 2007, Mysterud 2012, Lindsey et al. 2013. Additionally, shifts in the proportion of unique phenotypes (Wilfred 2012, Monteith et al. 2013, Rivrud et al. 2013, Coulson et al. 2018, LaSharr et al. 2019b or behavioral traits (Singer andZeigenfuss 2002, Leclerc et al. 2019) also may occur. Considerable speculation exists about the biological effects of trophy hunting, but much remains unknown (Harris et al. 2002, Festa-Bianchet and Lee 2009, Festa-Bianchet 2016, Festa-Bianchet and Mysterud 2018. ...
Reported effects of trophy harvest often are controversial. The subject is nuanced and many studies lack details necessary to place their results in context. Consequently, many studies are misunderstood or their conclusions misapplied. We propose that all dialogues about trophy hunting include a definition of how they use the term trophy, details of variables measured and why they were selected, and explanations of temporal and spatial scales employed. Only with these details can potential effects of trophy hunting be understood in context and used for management and policy decisions. © 2021 The Wildlife Society. Effects of trophy harvest often are controversial because many studies lack important details. Dialogues about trophy hunting must include a definition of how they use the term trophy, details of variables measured and why they were selected, and explanations of temporal and spatial scales employed so that potential effects of trophy hunting can be understood in context.
... Trophy hunting is highly selective as it targets the limited preferred species as informed by the set hunting quotas for the targeted animals in a population with outstanding characteristics, such as horns, tusks, body size and skull length. This is distinguished from predation where the predator targets the weakest individual in the prey population (Bothma and Bothma 2006;Lindsey et al. 2006;Rivrud et al. 2013) hypothesised that trophy hunters will consistently target good quality prime-aged individual wild animals, therefore the young or weaker adults will have the responsibility to reproduce. Hence, although sport hunting plays an important role in the dynamics of ungulate populations, it can result in increased mortality and reduced life expectancy, with older animals becoming rare (Damm 2008;Funston 2011;Batavia et al. 2019). ...
... Trophy hunting is highly selective as it targets the limited preferred species as informed by the set hunting quotas for the targeted animals in a population with outstanding characteristics, such as horns, tusks, body size and skull length. This is distinguished from predation where the predator targets the weakest individual in the prey population (Bothma and Bothma 2006;Lindsey et al. 2006;Rivrud et al. 2013) hypothesised that trophy hunters will consistently target good quality prime-aged individual wild animals, therefore the young or weaker adults will have the responsibility to reproduce. Hence, although sport hunting plays an important role in the dynamics of ungulate populations, it can result in increased mortality and reduced life expectancy, with older animals becoming rare (Damm 2008;Funston 2011;Batavia et al. 2019). ...
This study was based on a temporal analysis of trophy quality trends and hunting effort in Chewore South Safari Area (CSSA), Zimbabwe, for the period 2009-2012. We selected four of the big five species, namely; buffalo (Syncerus caffer), elephant (Loxodonta africana), the leopard (Panthera pardus) and lion (Panthera leo) for analysis. Existing database of 188 trophies from 2009 to 2011 was reviewed and recorded using the Safari Club International (SCI) scoring system. Further, 50 trophies for 2012 were measured and recorded based on the SCI scoring system. Local ecological knowledge on trophy quality and hunting effort in CSSA was obtained through semi-structured questionnaires from 22 conveniently selected professional hunters in 2012. The results indicated no significant change in trophy quality trends of buffalo, leopard and lion (p > 0.05) over the study period. In contrast, there was a significant decline in elephant trophy quality trend over the same period (p < 0.05). The results showed no significant change in hunting effort over the study period for all the four study species (p > 0.05). Furthermore, seventy-two percent (72%, n = 13) of the professional hunters confirmed that elephant population was declining in CSSA and this was likely due to poaching. Professional hunters perceived trophy hunting as a source of financial capital generation for wildlife conservation (61%, n = 11), as well as positively contributing to the local economy (56%, n = 10). It was concluded that hunting has limited negative impact on species trophy quality trends when a sustainable hunting system is consistently followed in CSSA. CSSA management need to continuously monitor trophy hunting, animal populations and employ adaptive management approach to quota setting and species conservation.
... Behavioural responses of prey can be more strongly affected by hunting risk than risk induced by predators (Proffitt et al., 2009), but depend on the context (Ciuti et al., 2012). Consistent and strong harvest selection by hunters can even profoundly affect morphological and reproductive traits of species in a negative way (Darimont et al., 2009, but see Rivrud et al., 2013) or oppose natural selection (Carlson et al., 2007). We did not find any effect of hunting risk on reproductive output, possibly because of the restricted period in which hunting took place, or because of the effects of adverse weather (Van Wieren et al. 2006). ...
... Their number increases ( Csányi, 1995;Bieberm and Ruf, 2005; Geisser and Reyer, 2006), which probably affects also Wild Boar population in Serbia. Despite positive changes in Red Deer and Wild Boar populations, Serbian hunting sector is still low-abundant with ungulate population in comparison with other European countries ( Milner et al., 2006;Apollonio et al., 2010;Rivrud et al., 2013). The findings indicate that the number of Roe Deer in Serbia dropped, and that nowadays it is slightly higher than in 2001. ...
... Likewise, in the absence of harvest restrictions, sheep hunters harvesting the largest males are often taking the oldest in the population and not exerting a strong unidirectional selection against males with superior genetic potential (Frisina and Frisina 2012). Declines in horn and antler size often reflect a declining male age composition in hunted populations (Schmidt et al. 2007, Monteith et al. 2013, Rivrud et al. 2013. Except in limited cases, trophy hunters do not impose intensive selection by removing the largest males in each age class but rather the largest they are able to harvest during the hunting season, during daylight hours, in the areas they are allowed to hunt, and on the days they are afield. ...
Differentially harvesting individual animals with specific traits has led some to argue that such selection can cause evolutionary change that may be detrimental to the species, especially if those traits are related positively to individual fitness. Most hunters are not selective in the type of animal they take, satisfied instead to harvest any legal animal. In a few exceptions, however, regulations may limit hunters to harvest animals of a minimum size or age regardless of their personal choice. Using information from a broad range of aquatic and terrestrial systems exposed to a myriad of potential and operational selective pressures, several authors have made expansive generalizations about selective harvest and its applicability to ungulates. Harvest-based selection can potentially be intensive enough to be relevant in an evolutionary sense, but phenotypic changes consistent with hunter selection are otherwise confounded with multiple environmental influences. Factors such as age, genetic contribution of females, nutrition, maternal effects, epigenetics, patterns of mating success, gene linkage, gene flow, refugia, date of birth, and other factors affecting selection interact with harvest to impede unidirectional evolution of a trait. The intensity of selection determines potential for evolutionary change in a meaningful temporal framework. Indeed, only under severe intensity, and strict selection on a trait, could human harvest prompt evolutionary changes in that trait. Broad generalizations across populations or ecological systems can yield erroneous extrapolations and inappropriate assumptions. Removal of males expressing a variety of horn or antler sizes, including some very large males, does not inevitably represent directional artificial selection unless the selective pressures are intensive enough to cause a unidirectional shift in allele frequencies that may act on some relevant life-history trait or process. Here I review the topic of harvest-based selection in male ungulates and discuss the inefficiency of trophy hunting in changing genetic expression of phenotype. © 2017 The Wildlife Society.
... Evolutionary change would be more rapid if both sexes were selectively targeted as is unfortunately the case for African elephant (Loxodonta africana) populations in some countries (Selier et al. 2014). When harvesting is less selective, or coupled with habitat change, the evolutionary consequences of selective harvesting may be harder to detect (Garel et al. 2007, Crosmary et al. 2013, Monteith et al. 2013, Rivrud et al. 2013). Our work does not tackle the ethics or ecological consequences of trophy hunting, nor do we account for potential economic benefits of hunting for local communities, whether these be in Canada (Hurley et al. 2015) or in the developing world (Lindsey et al. 2007). ...
Some ecologists suggest that trophy hunting (e.g., harvesting males with a desirable trait above a certain size) can lead to rapid phenotypic change, which has led to an ongoing discussion about evolutionary consequences of trophy hunting. Claims of rapid evolution come from the statistical analyses of data, with no examination of whether these results are theoretically plausible. We constructed simple quantitative genetic models to explore how a range of hunting scenarios affects the evolution of a trophy such as horn length. We show that trophy hunting does lead to trophy evolution defined as change in the mean breeding value of the trait. However, the fastest rates of phenotypic change attributable to trophy hunting via evolution that are theoretically possible under standard assumptions of quantitative genetics are 1–2 orders of magnitude slower than the fastest rates reported from statistical analyses. Our work suggests a re-evaluation of the likely evolutionary consequences of trophy hunting would be appropriate when setting policy. Our work does not consider the ethical or ecological consequences of trophy hunting.
... In several ungulate populations in Europe and North America, sport hunting is the main cause of adult mortality (Langvatn & Loison 1999;McCorquodale 1999;Ballard et al. 2000;Festa-Bianchet 2003;Mysterud, Solberg & Yoccoz 2005;Milner et al. 2006). Harvest may have strong effects on population dynamics (Milner, Nilsen & Andreassen 2007;Femberg & Roy 2008), and potential evolutionary effects on phenotype and life-history traits [ (Proaktor, Coulson & Milner-Gulland 2007;Pigeon et al. 2016), but see (Mysterud 2011;Rivrud et al. 2013)]. In ungulates, survival of adult females has higher elasticity for population growth compared to reproductive parameters or to survival of other age-sex classes (Gaillard, Festa-Bianchet & Yoccoz 1998;Gaillard et al. 2000). ...
Female ungulates are often selectively harvested according to their reproductive status. Because ungulate population growth depends heavily on adult female survival, it is crucial to understand the effects of this selective harvest. Recent studies revealed persistent individual differences in female reproductive potential, with a positive correlation of reproductive success over consecutive years. If current reproduction is correlated with lifetime reproductive success, then selective harvest of non‐lactating females should remove individuals of low reproductive potential, with lower impact on population growth than random harvest. If lifetime reproductive success has a genetic basis, selective harvest may also increase the proportion of successful females.
We used an individual‐based model to understand the short‐term effects of harvest intensity and hunter selectivity on population dynamics, accounting for both heterogeneity in reproductive potential and orphan survival. We also explored the long‐term effect of harvest as a selective pressure on female heterogeneity.
Selective harvest of non‐lactating females reduced survival to primiparity compared to random harvest, because of high harvest rates of pre‐reproductive females. After primiparity, however, females of higher reproductive potential had higher survival under selective than random harvest. Therefore, the overall effect on population dynamics depends on a trade‐off between a high harvest of pre‐reproductive females and a reduced harvest of reproductive females with high reproductive potential.
Female heterogeneity and the length of the pre‐reproductive period affected this trade‐off. Over the short term, high heterogeneity in reproductive potential of pre‐reproductive females made selective harvest the most effective strategy to maintain a high population growth rate. With low heterogeneity and little effects of orphaning on juvenile mortality, however, random harvest had a lower impact on population growth than selective harvest. Over the long term, selective female harvest may increase the proportion of successful reproducers in the population.
Synthesis and applications . Selective harvests of non‐lactating females appear justified only if female heterogeneity in reproductive potential and/or orphan mortality are very high. Because pre‐reproductive females will be subject to intense harvest, selective harvest may reduce population growth rate compared to random harvest in species with late primiparity, especially if most pre‐reproductive female normally survive to primiparity. When heterogeneity in reproductive potential and orphan mortality are low, random female harvest appears preferable to selective harvest.
... If persisting over a few tens of generations, this may lead to undesirable human-induced evolution. Concerns regarding the sustainability of the growing trophy hunter industry are increasing (22), although some cultures already have practices to avoid such undesirable effects (23). Our study identifies two practical levers by which policy makers could address selectivity: the duration of the hunting season and the number of hunters that compete for a given quota. ...
Significance
Wildlife populations in Europe and North America are regulated through hunting, as natural predators are still scarce. Therefore, wildlife is a social–ecological system with delicate feedbacks between the social and ecological subsystems. Both for population control and for evolution and because of cultural values, it is essential to understand how many and which animals are removed from the population. However, the question of how the social context influences the individual hunter’s decision to shoot or not to shoot an animal has not been addressed. We apply insights from economic search theory to explain how hunter selection is shaped by social constraints. We provide convincing evidence, using a unique dataset from deer hunting, that selectivity declines with more hunters competing and a shorter remaining season.
... Such data, however, are not always available, owing to the high costs and logistic difficulties of monitoring programmes. Therefore, large datasets from hunting records are commonly used to obtain biological information [1,2]. This practice has been criticized, because data from hunt-killed animals may be biased [3], because hunters almost always select individuals from populations non-randomly, selecting primarily adults, sometimes as large as possible. ...
Quantifying temporal changes in harvested populations is critical for applied and fundamental research. Unbiased data are required to detect true changes in phenotypic distribution or population size. Because of the difficulty of collecting detailed individual data from wild populations, data from hunting records are often used. Hunting records, however, may not represent a random sample of a population. We aimed to detect and quantify potential bias in hunting records. We compared data from a long-term monitoring project with hunting records of brown bears (Ursus arctos) in Sweden and investigated temporal trends (1996–2013) in the ratio of yearlings to adult females, yearling mass and adult female mass. Data from hunting records underestimated the decline in yearling and adult female mass over time, most likely owing to the legal protection of family groups from hunting, but reflected changes in the ratio of yearlings to adult females more reliably. Although hunting data can be reliable to approximate population abundance in some circumstances, hunting data can represent a biased sample of a population and should be used with caution in management and conservation decisions.
... For example red deer (Cervus elaphus) do not reach full antler size until they become successful breeders, and continue to grow large antlers even after they enter reproductive senescence (Kruuk et al. 2002). Therefore, a moderate level of trophy hunting may not remove many stags before they have a chance to breed, and there is no evidence of a temporal decline in antler size for this species (Rivrud et al. 2013). our knowledge of how selective hunting may affect the distribution of matings, however, is limited by the very small number of ungulate species with reliable data on age-specific male reproductive success (Festa-Bianchet 2012). ...
... Johnson et al., 2010). There have also been numerous studies which have Similarly, Livengood (1983) and Wennergren et al (1977) (Rivrud et al., 2013;Packer et al., 2009), in order to ensure that the offtake does not result in eventual trophy size reduction. Similarly, if hunting packages in relatively wild, unspoiled places generate significantly more revenue than others, then that is important knowledge for developing future packages and provides further economic incentives to maintain those areas. ...
The trophy hunting of African leopards Panthera pardus pardus may generate revenue to help foster their conservation. However, leopards are sensitive to hunting and populations decline if overharvested. The practice therefore requires careful management grounded in robust estimates of population density/status. Camera-trap surveys are commonly used to establish leopard numbers, and may guide harvest quotas. However, such surveys are limited over wide spatial scales and many African governments lack resources to implement them.
In this thesis I explore the potential use of a harvest composition scheme applied to puma Puma concolor in North America, to monitor leopards. The method hinges on the susceptibility of different leopard cohorts to hunting and if this varies, then predictions can be made about harvest composition. Susceptibility is likely to be governed by space use, encounter rates with bait lures (a common method used to attract leopards to hunting hides) and hunter selectivity. Thus in this thesis I explore leopard susceptibility to these factors using a protected leopard population in northern Zululand, South Africa. In my first chapter I examine using scent lures in camera-trapping. Against a backdrop of a passive survey I show adult males, females and sub-adults are captured at similar rates compared to a passive survey using lures. The use of lures does not appear to violate closure assumptions or affect spatio-temporal patterning, but their use appears limited as density estimate precision is not improved. My second chapter examines ecological (likelihood of encountering a hunter) and anthropogenic (attractiveness to hunters) susceptibility of leopards to trophy hunting. I show that adult males are the most susceptible cohort to hunting (sub-adults least susceptible). I then take the incident rates from ecological and anthropogenic models and create a theoretical harvest composition using population parameters of protected leopards.
My third data chapter departs from hunting susceptibility and examines determinants of leopard trophy package price across Africa. I show that factors such as trophy quality, outfitter leopard hunting reputation and hunt success have little impact on price determination. Instead, overall outfitter reputation and the number of charismatic species in a package are positively correlated with price. These results have important consequences on several sustainable leopard hunting schemes proposed in the literature.
... To enable more targeted management it is also important to understand population processes and effects of exploitation on life-history parameters [2][3][4][5][6]. Depending on the life-history and social structure of the species in question, harvesting techniques and motivations for harvesting (livelihood, commercial or sport) can affect size/age classes and sexes differently [7][8][9]. In addition, in migratory populations, or populations with a wide geographical distribution, varying harvest policies among regions or countries within the range can affect subsets of a given population differently [10]. ...
To sustainably exploit a population, it is crucial to understand and reduce uncertainties about population processes and effects of harvest. In migratory species, management is challenged by geographically separated changing environmental conditions, which may cause unexpected changes in species distribution and harvest. We describe the development in the harvest of Svalbard-breeding pink-footed geese (Anser brachyrhynchus) in relation to the observed trajectory and migratory behaviour of the population. In autumn, geese migrate via stopover sites in Norway and Denmark (where they are hunted) to wintering grounds in the Netherlands and Belgium (where they are protected). In Denmark and Norway harvesting increased stepwise during the 2000s. The increase in the population size only partly explained the change. The change corresponded to a simultaneous stepwise increase in numbers of geese staging in Denmark throughout autumn and winter; geese also moved further inland to feed which collectively increased their exposure to hunting. In Norway the increase in harvest reflected greater utilisation of lowland farmland areas by geese, increasing their hunting exposure. The study demonstrates how changes in migratory behaviour can abruptly affect exposure to hunting, which showed a functional response to increased temporal and spatial availability of geese. The harvest has now reached a level likely to cause a population decline. It highlights the need for flexible, internationally coordinated hunting regulations and reliable up-to-date population estimates and hunting bag statistics, which are rare in European management of migratory waterbirds. Without such information decisions are left with judgments based on population estimates, which often have time lags of several years between recording and reporting, hampering possibilities for the timely adjustment of management actions.
... Populations of hunters consist of different types, each with different goals and preferences, that is, some hunting mainly for trophies, others for meat, for population control and more. Groups of hunters with different motivations can differ largely in their effectiveness (Andersen et al. 2014), and hunter behavior through different methods (Martinez et al. 2005;Torres-Porras et al. 2009) or categories of hunters Rivrud et al. 2013) can influence the composition of the harvest. Knowledge about heterogeneity and dynamics among hunters and their corresponding variation in hunter preference should therefore be incorporated when formulating management rules. ...
Most cervid populations in Europe and North America are managed through selective harvesting, often with age- and sex-specific quotas, with a large influence on the population growth rate. Less well understood is how prevailing weather affects harvesting selectivity and off-take indirectly through changes in individual animal and hunter behavior. The behavior and movement patterns of hunters and their prey are expected to be influenced by weather conditions. Furthermore, habitat characteristics like habitat openness are also known to affect movement patterns and harvesting vulnerability, but how much such processes affect harvest composition has not been quantified. We use harvest data from red deer (Cervus elaphus) to investigate how weather and habitat characteristics affect behavioral decisions of red deer and their hunters throughout the hunting season. More specifically, we look at how sex and age class, temperature, precipitation, moon phase, and day of week affect the probability of being harvested on farmland (open habitat), hunter effort, and the overall harvest numbers. Moon phase and day of week were the strongest predictors of hunter effort and harvest numbers, with higher effort during full moon and weekends, and higher numbers during full moon. In general, the effect of fall weather conditions and habitat characteristics on harvest effort and numbers varied through the season. Yearlings showed the highest variation in the probability of being harvested on farmland through the season, but there was no effect of sex. Our study is among the first to highlight that weather may affect harvesting patterns and off-take indirectly through animal and hunter behavior, but the interaction effects of weather and space use on hunter behavior are complicated, and seem less important than hunter preference and quotas in determining hunter selection and harvest off-take. The consideration of hunter behavior is therefore key when forming management rules for sustainable harvesting.
... Such harvesting can cause changes in the distribution of phenotypic traits within target populations, often with undesirable biological and economic consequences. For example, selective harvesting has been linked to declines in the size of trophy horns in two antelope species in Zimbabwe (2) and of antlers in red deer (Cervus elaphus) in Europe (3,4), as well as to earlier maturation in some fish species (5). However, the extent to which these changes are the result of ecological or evolutionary mechanisms has been much debated (1). ...
Selective harvesting of animals is widespread throughout the marine, freshwater, and terrestrial environments and affects a diverse list of species, including fish, mammals, birds, and reptiles (1). Such harvesting can cause changes in the distribution of phenotypic traits within target populations, often with undesirable biological and economic consequences. For example, selective harvesting has been linked to declines in the size of trophy horns in two antelope species in Zimbabwe (2) and of antlers in red deer (Cervus elaphus) in Europe (3, 4), as well as to earlier maturation in some fish species (5). However, the extent to which these changes are the result of ecological or evolutionary mechanisms has been much debated (1). In PNAS, Traill et al. (6) approach this question from a novel angle by developing stochastic two-sex integral projection models (IPMs) capable of differentiating between the ecological and evolutionary effects of selective harvest. Their finding that evolutionary mechanisms contribute relatively little to observed changes in the body mass of bighorn sheep (Ovis canadensis) is an intriguing contribution to the debate over the evolutionary consequences of selective offtake, contradicting earlier studies (7). In addition, Traill et al. (6) suggest that their method could be adopted more widely to allow wildlife managers and conservation practitioners to incorporate the potential evolutionary effects of selective harvesting into their management planning. Here, we explore this suggestion by discussing key challenges that would need to be addressed to translate the approach by Traill et al. (6) from a purely biological model to an effective management model, focusing particularly on issues of data availability and the incorporation of different forms of uncertainty.
... These hunters are partly interested in team hunting, partly interested in trophy hunting, and unlike the rural-dominated deer enthusiasts, more likely to live in urban areas, where we found the best potential for recruiting new hunters. By contrast, trophy hunters in Poland and Hungary (Rivrud et al. 2013) are typically foreign hunters with a high willingness to pay, whereas the local people more often target younger animals and females, which are more accessible at a lower price per license. Thus, in these countries, motivating the locals rather than the visitors would We denote explanatory variables (i.e., significant part of model estimation) with asterisks and show inactive covariates (supportive information, not part of model estimation) in light font. ...
In both North America and Europe, deer populations are increasing and hunter participation is decreasing. This generates concern for our future ability to control deer populations. Information on hunter typologies can help ascertain which licensing regulations are the most useful for either deer population control or activating currently non-active hunters. We used latent class analyses to identify typologies among 1,820 active and non-active red deer hunters in Norway. We found that active hunters could be grouped into mixed visitors (77%), deer enthusiasts (13%), and solitary locals (10%) in regard to their motivation and approach to hunting and landowner acquaintances (47%), less involved locals (40%), and long-term visitors (13%) when considering access to hunting grounds. We found 2 typologies of non-active hunters: likely recruits (79%) and permanently gone (29%). Managers in areas with undesirably dense deer populations should be more flexible in the way hunting is organized and promoted to motivate a diverse group of hunters. We recommend a zone-based management plan based on key factors determining hunter participation, which in our study included location of residence, interest in trophies, willingness to pay, willingness to travel, sociality, landowner relations, and leasing agreements. © 2014 The Wildlife Society.
... An increase in age over time was reported for trophy-harvested Iberian wild goats (Pérez et al. 2011) in Spain and Rocky Mountain bighorn rams in British Columbia (Hengeveld and Festa-Bianchet 2011). In contrast, reduced postwar harvest of red deer (Cervus elaphus) in Hungary led to an increase in antler length and number of tines of the very largest harvested stags (Rivrud et al. 2013). Because the antlers of only the largest stags were measured, however, it is unclear how different harvest strategies affected antler size at the population level (Pelletier et al. 2012). ...
Long-term data (1974–2011) from harvested bighorn rams (Ovis canadensis) in Alberta, Canada, suggested a reduction in horn size and in the proportion of trophy rams in the provincial population over time. Age at harvest increased over time, suggesting slower horn growth. Rams that experienced favorable environmental conditions early in life had rapid horn growth and were harvested at a younger age than rams with slower horn growth. Guided nonresident hunters did not harvest larger rams than residents, suggesting that few large rams were available. Resident hunter success declined in recent years. Despite an apparently stable population, successive cohorts produced a decreasing harvest of trophy rams. We suggest that unrestricted harvest based on a threshold horn size led to a decline in the availability of trophy rams. That decline is partly an inevitable consequence of selective hunting that removes larger rams. Although our analysis does not establish that evolution of smaller horns caused the observed decline in both horn size and harvest of trophy rams, we suggest that intensive trophy hunting may have artificially selected for a decrease in horn growth rate. © 2013 The Wildlife Society.
... Human hunting influences animal movements, resource selection, and population dynamics of wildlife (Lindsey et al. 2007; Juillet et al. 2012). Most management-oriented research has traditionally focused on the evolutionary consequences of selective hunting on the population dynamics of wildlife (Coltman et al. 2003; Servanty et al. 2011; Rivrud et al. 2013). However, few studies have considered the direct and indirect implications of hunting for managing disease risk in wild populations (Wasserberg et al. 2009; Wild et al. 2011). ...
Endemic and emerging diseases are rarely uniform in their spatial distribution or prevalence among cohorts of wildlife. Spatial models that quantify risk-driven differences in resource selection and hunter mortality of animals at fine spatial scales can assist disease management by identifying high-risk areas and individuals. We used resource selection functions (RSFs) and selection ratios (SRs) to quantify sex- and age-specific resource selection patterns of collared (n = 67) and hunter-killed (n = 796) nonmigratory elk (Cervus canadensis manitobensis) during the hunting season between 2002 and 2012, in southwestern Manitoba, Canada. Distance to protected area was the most important covariate influencing resource selection and hunter-kill sites of elk (AICw = 1.00). Collared adult males (which are most likely to be infected with bovine tuberculosis (Mycobacterium bovis) and chronic wasting disease) rarely selected for sites outside of parks during the hunting season in contrast to adult females and juvenile males. The RSFs showed selection by adult females and juvenile males to be negatively associated with landscape-level forest cover, high road density, and water cover, whereas hunter-kill sites of these cohorts were positively associated with landscape-level forest cover and increasing distance to streams and negatively associated with high road density. Local-level forest was positively associated with collared animal locations and hunter-kill sites; however, selection was stronger for collared juvenile males and hunter-killed adult females. In instances where disease infects a metapopulation and eradication is infeasible, a principle goal of management is to limit the spread of disease among infected animals. We map high-risk areas that are regularly used by potentially infectious hosts but currently underrepresented in the distribution of kill sites. We present a novel application of widely available data to target hunter distribution based on host resource selection and kill sites as a promising tool for applying selective hunting to the management of transmissible diseases in a game species.
Hunter-collected data and samples are used as indices of population performance, and monitoring programs often take advantage of such data as ecological indicators. Here, we establish the relationships between measures of skeleton size (lower jawbone length and hind-leg length) and autumn carcass mass of slaughtered individuals of known age and sex of the high Arctic endemic Svalbard reindeer ( Rangifer tarandus platyrhynchus ). We assess these relationships using a long-term monitoring dataset derived from samples of hunted or culled reindeer. The two skeleton measures were generally strongly correlated within age class. Both jaw length ( R ² = 0.78) and hind-leg length ( R ² = 0.74) represented good proxies of carcass mass, but these relationships were mainly driven by an age effect (i.e., due to growth). The skeleton measures reached an asymptote at 4–6 years age. Accordingly, strong positive correlations between skeleton measures and carcass mass were mainly evident in young age classes (range r [0.45–0.84] for calves and yearlings), while in adult age classes, these relationships weakened due to skeletal growth ceasing in mature animals as well as the strong impacts of annual environmental fluctuations, causing increased variance in mass with age. Although body mass is often viewed as the ‘gold standard’ in ungulate monitoring, our results indicate that skeleton measures collected by hunters may provide similar valuable information about variation in ecological processes, particularly for the younger age classes. Such harvest-based monitoring proxies may improve the management’s access to indicators of changing environmental conditions.
Introduction:
Over recent decades, the abundance and geographic ranges of wild ungulate species have expanded in many parts of Europe, including the UK. Populations are managed to mitigate their ecological impacts using interventions, such as shooting, fencing and administering contraception. Predicting how target species will respond to interventions is critical for developing sustainable, effective and efficient management strategies. However, the quantity and quality of evidence of the effects of interventions on ungulate species is unclear. To address this, we systematically mapped research on the effects of population management on wild ungulate species resident in the UK.
Methods:
We searched four bibliographic databases, Google Scholar and nine organisational websites using search terms tested with a library of 30 relevant articles. Worldwide published peer-reviewed articles were considered, supplemented by 'grey' literature from UK-based sources. Three reviewers identified and screened articles for eligibility at title, abstract and full-text levels, based on predefined criteria. Data and metadata were extracted and summarised in a narrative synthesis supported by structured graphical matrices.
Results:
A total of 123 articles were included in the systematic map. Lethal interventions were better represented (85%, n = 105) than non-lethal interventions (25%, n = 25). Outcomes related to demography and behaviour were reported in 95% of articles (n = 117), whereas effects on health, physiology and morphology were studied in only 11% of articles (n = 14). Well-studied species included wild pigs (n = 58), red deer (n = 28) and roe deer (n = 23).
Conclusions:
Evidence for the effects of population management on wild ungulate species is growing but currently limited and unevenly distributed across intervention types, outcomes and species. Priorities for primary research include: species responses to non-lethal interventions, the side-effects of shooting and studies on sika deer and Chinese muntjac. Shooting is the only intervention for which sufficient evidence exists for systematic review or meta-analysis.
Some ecologists suggest that trophy hunting (e.g. harvesting males with a desirable trait above a certain size) can lead to rapid phenotypic change, which has led to an ongoing discussion about evolutionary consequences of trophy hunting. Claims of rapid evolution come from the statistical analyses of data, with no examination of whether these results are theoretically plausible. We constructed simple quantitative genetic models to explore how a range of hunting scenarios affects the evolution of a trophy such as horn length. We show that trophy hunting does lead to trophy evolution defined as change in the mean breeding value of the trait. However, the fastest rates of phenotypic change attributable to trophy hunting via evolution that are theoretically possible under standard assumptions of quantitative genetics are 1 to 2 orders of magnitude slower than the fastest rates reported from statistical analyses. Our work suggests a re-evaluation of the likely evolutionary consequences of trophy hunting would be appropriate when setting policy. Our work does not consider the ethical or ecological consequences of trophy hunting.
Intra- and intersexual selection drives the evolution of secondary sexual traits, leading to increased body size, trait size and generally increased reproductive success in bearers with the largest, most attractive traits. Evolutionary change through natural selection is often thought of primarily in terms of genetic changes through mutations and adaptive selection. However, this view ignores the role of the plasticity in phenotypes and behaviour and its impact on accelerating or decelerating the expression of sexually selected traits. Here, we argue that sudden changes in selection pressures (e.g. predation pressure) may cause a cascade of behavioural responses, leading to a rapid change in the size of such traits. We propose that selective removal of individuals with the most prominent traits (such as large antlers or horns in male ungulates) induces behavioural changes in the surviving males, leading to a reduction in the growth of these traits (phenotypic expression). To test this idea, we used an individual-based simulation, parametrized with empirical data of male bighorn sheep, Ovis candensis. Our model shows that the expression (phenotype, not genotype) of the trait under selection (here horn size) can be negatively impacted, if the biggest, most dominant males in the population are removed. While the selective removal of prime males opens breeding opportunities for younger, smaller males, we predicted that it would come at the expense of growth and maintenance. As predicted, we observed a rapid decline in average male horn length in our model. We argue that this decline happens because smaller males, instead of allocating energy into growth, divert this energy towards participation in mating activities that are typically exclusively available to prime males. While our model deals with ecological life-history trade-offs, it cannot predict evolutionary outcomes. However, this nongenetic mechanism is important for the understanding of evolutionary processes because it describes how heritable traits can rapidly change because of behavioural plasticity, long before any genetic changes might be detectable.
The study evaluates the impact of climatic factors on the success of hunting in the Doupov Hills in the Czech Republic. The aim was to assess the impact of climatic factors on the success of individual and group hunting of various game species and their sex and age between 2005–2012. Overall, 27 thousand animals of the following game species were analyzed: red deer (Cervus elaphus L.), sika deer (Cervus nippon Temminck), fallow deer (Dama dama L.), mouflon (Ovis musimon L.), roe deer (Capreolus capreolus L.), wild boar (Sus scrofa L.), European badger (Meles meles L.) and red fox (Vulpes vulpes L.). The results show that mostly temperature co-determines the success of both hunting methods. Atmospheric pressure represents another important factor of influence, especially in group hunting. Snow cover supports variability of the probability of game hunting success. The success of hunting increased with decreasing temperature, increasing snow cover and increasing atmospheric pressure. Conversely, precipitation and wind speed had low effect on the success of hunting. Individual hunting was associated with significantly better climatic conditions in comparison to group hunting. Moreover, male game species were hunted in more favourable climatic conditions compared to female. Findings on the influence of climatic factors on the success of hunting can support planning the suitable time and method of hunting, thus increasing the success of hunting in montane and submontane regions of Central Europe.
The assessment of the trophy quality in Fallow deer (Dama dama) is often based on the measured values of the individuals with the largest antlers. However, there is little knowledge about the reliability and representativity of this approach. In our study, we analysed the trend of the annual number of evaluated trophies between 1998 and 2016, the age distribution of the harvested bucks, and the temporal variation in the values of trophy weight and antler length during the study period on the population level and in the case of the best quality antlers. The data were examined in 3 estimated age classes (young: up to 4 yrs, middle-aged: 5-9 yrs, old: from 10 yrs). The groups (year × age class) were characterized by the median, while the largest values were picked in each group by selecting the lowest value among the individuals belonging to the upper 1%, 5% and 10% of the sample size. The annual number of the presented trophies increased from 894 to 3,795 with an exponential trend. The proportion of the age classes changed significantly. The proportion of the young bucks increased by 10.2%, while the proportion of the middle-aged individuals decreased by 9.9%. The median of the weight showed no trend in the complete dataset. In the young age class, it increased until 2006, then decreased until 2016. In case of the middle-aged and old individuals, the median and the strongest values at each threshold also increased. The median of the complete dataset, as well as the middle-aged and old bucks, stagnated in the case of antler length. It showed an 8.5 cm decrease between 2007 and 2016 in the young age class. In general, the difference between the group median and the largest values showed the highest variability in case of the 1% threshold. We found a strong correlation between the group median and the strongest values only in two cases (Top 10% and 5% threshold, trophy weight of middle-aged bucks). Our results suggest that in Fallow deer, the assessment of the trophy quality based on only the largest antlers may be misleading in several cases, especially in the young age class or if the complete dataset is treated as one group. However, the trend of the largest trophy weight in the middle-aged and old age classes may refer to the trend of the median in the relevant groups.
Trophy hunting, the selective removal of animals for human recreation, can contribute to conservation when appropriately managed. Yet, little is known about how harvest rates or different definitions of trophy affect age structure and trophy size in harvested animals and in survivors because no controlled studies exist. To investigate the impacts of different management regimes, we developed an individual-based model for bighorn sheep (Ovis canadensis), based on empirical data on survival from a protected population and data on horn growth from 2 populations that differed in their growth rates. One population showed slow horn growth and the other population fast horn growth. We subjected these model populations to varying harvest rates and 2 different hunting regulations: 4/5 curl and full-curl definitions of a trophy male. We found that the effect of hunting regulations depends on horn growth rate. In populations with fast horn growth, the effects of trophy hunting on male age structure and horn size were greater and the effect of a change in the definition of legal male smaller than in populations with slow growth rates. High harvest rates led to a younger age structure and smaller horn size. Both effects were weakened by a more restrictive definition of trophy male. As harvest rates increased past 40% of legal males, the number of males harvested increased only marginally because an increasing proportion of the harvested males included those that had just become legal. Although our simulation focused on bighorn sheep, the link between horn growth rate and harvest effects may be applicable for any size-selective harvest regime.
This chapter focuses on antelopes, a group of species within the family Bovidae. It focuses on Africa since this is where most research on trophy hunting of ungulates has been carried out. The chapter describes purely recreational hunting which is more common among local people in Europe, North America, and Australia. It also reviews more recent research on trophy hunting with a focus on the ecological and evolutionary effects of hunting on target species, and on the socio-economic drivers of trophy hunting and its impact on poverty alleviation. The chapter then considers the ways to improve the sustainability of trophy hunting. If sustainability can be improved through an understanding of the holistic nature of the hunting system, then the case for trophy hunting as a conservation tool can be considered based on its intrinsic merits, rather than with respect to issues surrounding its implementation in practice.
In Denmark, red deer (Cervus elaphus) are legal quarry (subject to no quotas) throughout the hunting season (1 September – 31 January) for anyone holding a valid license to hunt on their own land (more than 1 hectare) or on rented ground (larger than 5 hectares). As a consequence, in most parts of Denmark, multiple land owners and hunters on rented ground compete for the same individuals without any overall plan or coordination of the culling of local populations. The disadvantages of such a lack of management (for instance, the apparent deficit of mature stags because of high hunting pressure before reaching maturity) have been debated for decades. To contribute factual information to this debate, the demographic composition of two Danish red deer populations with contrasting land owner structure and hunting regimes were analysed and compared, from Djursland (hunting seasons 2008/9-2012/13) and Oksbøl red deer reserve (1985/86-2012/13). Djursland (1417 km2, the easternmost tip of Jutland) represents a ‘typical’ Danish landscape, comprising multiple owners of small or larger estates each of which run their own hunting practices. In this area, 1-year old males were protected in an effort to increase the proportion of mature stags in the population. During a five-year period, hunters on Djursland voluntarily delivered jaws from hunted red deer for age determination and morphometric information. The population on the Oksbøl red deer reserve (163 km2, south western Jutland) is managed by the Danish Nature Agency, with the aim of maintaining a stable red deer population with a high proportion of mature stags through a deliberate harvesting policy. On Oksbøl, the age of all harvested and deer found dead had been estimated on the basis of teeth wear (although the validity of this locally developed age estimation method had never been tested on independent data).
The aims of this analysis were (i) to test and calibrate the wear-based age es-timation method used on Oksbøl against independent data, (ii) to describe the demographic composition of the two populations from age at death dis-tributions, and (iii) to establish population models from this information. Since data was also available on the number of points on antlers, weight, pregnancy and lactation rates, relationships between these variables and age, population density and date were also calculated.
In summary, the results are as follows:
1. From a reference material of 37 individuals of known age (marked before 2 years old), true age correlated closely (R2 = 97%) and accurately (no bias) with age estimated from the number of incremental lines in teeth ce-mentum layers (‘method 1’), although with a precision of ±2 years for any given individual. Age estimation based on dentin layers can thus be con-sidered as a reliable method to estimate age of Danish red deer.
2. Age estimated from tooth wear in 15 red deer from Oksbøl correlated closely with age estimated from dental lines (R2 = 92 %). However, the age estimated from the number of dentin lines was on average 49.5 % higher (p< 0.0001) than that estimated from tooth wear, suggesting that the locally developed wear based age determination method systematically underestimated the age of dead red deer. A deer estimated to be 10 years old on the basis of the tooth wear method would, on average, be estimated to be 15 years old from counts of dentin lines.
3. The demographic composition of the Oksbøl population was constructed based on life tables established from 4278 aged females and 2896 males which died between 1990/91 and 2012/13. Females had an estimated annual mortality (based on adjusted age distribution from method 2 cal-culated at the start of the hunting season) of 33% as calves and 15-20% for all older age classes. This was equivalent to a spring population of females which consisted of 19% yearlings/calves from the preceding summer, 13% 2-year olds, 11% 3-year olds and 55% 4+ year olds. Males had an estimated annual mortality of 45% for calves, 35% for 1-3 year olds, and 20% for stags from 4 years of age, equivalent to an male age composition of 26% yearlings, 17% 2-years olds, 11% 3-years olds, 26% 4-7 year olds and 21% of 8 years of age or older. At the start of the rutting season, the population consisted of 2.6 hinds (i.e. females aged 1½ years old or older) for every stag aged 2½ years or more and 5.7 hinds for every stag aged 5½ year or more.
4. The demographic composition of the Djursland population was con-structed based on life tables established from 895 aged females and 622 males which died between 2008/09 and 2012/13. Seventy-four unsexed calves where assumed to represent an even sex distribution and were di-vided equally within the male and female life tables. Females had an es-timated annual mortality (calculated from the start of the hunting season) of 23% as calves and 20% as 1-7 year olds, and 34 of 8 years of age or older. This was equivalent to a spring female population of 22% yearlings/calves from the preceding summer, 18% 2-year olds, 15% 3-year olds and 45% 4+ year olds. Males had an estimated annual mortality of 24% for calves, 4% for yearlings, 26% for 2-year olds, and about 50% for 3-7 years of age. An apparent reduction in annual mortality after 8 years of age (24%) may be an artefact caused by a few old stags escaped from captivity. The estimated age distribution of males in spring thus consisted of 29% yearlings, 28% 2-year olds, 21% 3-year olds, 11% 4 year olds and 11% of 5 years of age or older. At the start of the rutting season, the population consisted of 1.8 hinds for every stag aged 2½ year or more, and 8.1 hinds for every stag aged 5½ year or more.
5. The population effect of protecting 1-year old males from hunting on Djursland could not be estimated rigorously because of the lack of refer-ence material (because protection was implemented throughout the sam-pling period) but could be cautiously estimated as a difference in mortality between yearlings and calves and 2-year old stags of about 20%. Ac-cordingly, without the protection of yearling males from hunting, the number of all older age groups of males would probably be 20% lower than observed.
6. Male body weight increased with age until the 5th year on Djursland and 10th year at Oksbøl. In both populations, female body weights increased with age until their 3rd year. Females from Djursland weighed on average 12% more than females from Oksbøl (methodological differences pre-cluded comparisons of stags between populations). In both populations, calf weights increased by 6-7 kg for both sexes during the first 2 months of the hunting season. During the same period the weight of adult stags decreased because of rutting activities. Calves from the Oksbøl population weighed 8-9% less in those years (mid 1990s) when population density peaked at almost twice the size as in the 1980s and after 2000. In 1- and 2-year old males, there was a 12% difference in body weight between cohorts born during the highest and lowest population densities.
7. The number of antler points increased until 8-15 years of age, reaching an average of 11 but with considerable (±3) individual variation. In both populations 2/3 of all males had at least 10 points at 5 years of age and 80-90% had at least 10 points at 8 years of age. The proportion of stags with 14 points or more peaked at c.25% during 12-15 years of age.
8. In both population more females than males were reported amongst the grown individuals (Djursland: 60% females, Oksbøl: 58% females) even though the sex ratio amongst calves was close to unity. In Oksbøl, the female: male ratio varied from 50:50 for individuals from cohorts born during lowest population densities to 65:35 for cohorts born during greatest densities. Since the sex-ratio of (dead) calves did not vary signifi-cantly as a function of population density, the female biases sex ratio of adults is likely to reflect increased emigration of stags under dense popu-lation conditions. On Djursland, the apparent female-biased sex ratio in the population may be the result of a campaign aimed at ceasing the growth of the population by targeting hinds and/or lower reporting fre-quencies for stags than for hinds.
9. Data on pregnancy and lactation rates were available from Djursland only. Here, 88% of all hinds on Djursland were pregnant, divided between 64% amongst 1-year old and 91% of older hinds. At the start of the hunting season 79% of all hinds were lactating (i.e. being with calf), based on 57% of the 2-old and 82% of older hinds.
10. On the basis of estimated age specific mortalities for each population and observed fecundity on Djursland (extrapolated to Oksbøl), population growth rates were estimated to be =1.02 at Oksbøl and 1.00 at Djursland. Since the population at Oksbøl remained about the same from the 1980ies to 2012/13, the predicted positive growth rate for the Oksbøl population might be the result of the substituted fecundity rates in the model (taken from the Djursland population) exceeding the true rates of the Oksbøl population. A population model incorporating a fecundity rate estimated from Djursland and no hunting mortality (99% annual survival until 8th years of age, 80% annual survival after that age), predicted an annual population growth rate of =1.21, which is equal to a doubling of the population size in four years. Estimates are given for population growth rates under different combinations of female age specific annual survival.
11. The estimated population patterns for the Oksbøl and Djursland popula-tions are discussed in relation to five dominant (but partly opposing) population objectives to: (i) maximise the number of harvested individuals relative to the population size (‘game ranch model’), (ii) maximise the number of harvested mature stags relative to the size of the population (‘trophy model’), (iii) maintain a ‘high’ proportion of mature stags in the living population, (iv) attain a ‘sustainable’ harvesting (several defini-tions), and (v) sustain an intended ‘natural’ demographic composition.
12. In terms of number of harvested individuals relative to the size of the winter population, the populations at Oksbøl and Djursland resulted in a yield of 37 and 32 harvested individuals/ 100 individuals in the winter population. This was 55-60% of the maximum possible number of har-vested individuals in a population managed for that purpose (game ranch model: 62/100), about the same number as harvested in a population managed to maintain an intended natural demographic composition (34/100) and half the number harvested in a population managed to maximize the number of harvested stags of at least 8 years of age.
13. On Djursland, 0.4 mature stags (defined as at least 8 years of age) were harvested per 100 individuals in the spring population. This constitutes 4% of the harvest from a population managed to maximize the harvest of mature stags (trophy model: 8.7/100), 15% of the harvest from a popula-tion with an intended natural demographic composition (2.6/100) and one third the number of mature stags harvested at Oksbøl (1.2/100) or in a population managed in order to optimize meat harvest (game ranch model). Without protection of 1-year old males, the yield of mature stags would probably have been 20% lower than observed. In addition to providing hunters with a very low yield of mature stags, in an evolution-ary perspective, the low average longevity of stags on Djursland creates a real risk of selecting for earlier maturity and smaller body size.
14. Even though the harvest policy on Oksbøl resulted in a three times higher harvest of mature stags relative to the population size than on Djursland and a less biased ratio between the numbers of hinds and mature stags, a change in age-specific culling towards a higher harvest of calves and individuals older than 8 years compared to present would double the harvest of mature stags as well as their proportion of the live population. This would also be in line with the general mortality pattern observed in naturally regulated ungulate populations elsewhere.
15. If managers aim to increase the number of mature stags in the population as well as in the overall hunting yield, the most efficient tool would be to protect all immature stags from hunting until they have reached the re-quired size for harvest and mating.
The genetic diversity of Red Deer (Cervus elaphus) in Hungary was studied using a fall-length cytochrome b gene (1140 bp). The haplotype structure of this species was evaluated in the three main partially geographically separated populations in this country. Throughout the country, the genetic diversity of the Red Deer was represented by individuals belonging to all the three distinct mitochondrial lineages of this species in Europe, i.e. western, eastern and Sardinian/Bulgarian. The presence of all the three mtDNA lineages in the Red Deer populations in Hungary implied the existence of an overlapping zone among them. The genetic distinction between Red Deer populations inhabiting this zone showed the highest levels of dissimilarity of the northeast population. The recorded population genetic peculiarities and the geographical variability of cytochrome b gene haplotypes in Hungarian Red Deer as well as clarification of its phylogenetic relationships to other genetically characterised populations allowed us to identify its intraspecific population differences in Hungary.
Czech Republic has a long tradition of hunting, and trophy hunting is important to manage game populations. In this study data was analysed from the five last trophy exhibitions in Czech Republic. Namely, hunter selection, compensatory selection, management selection, hunting pressure selection and depletion selection was tested in different landscape types. In compensatory hunting there is a difference between the landscape types; apparent differences exist between the landscape type with respect to hunting pressure. There was no hunter selection, or depletion selection, and no differences in management between landscape types. This study suggests that the landscape composition has an effect on selective hunting in Czech Republic.
Moose Alces alces gigas in Alaska, USA, exhibit extreme sexual dimorphism, with adult males possessing large, elaborate antlers. Antler size and conformation are influenced by age, nutrition and genetics, and these bony structures serve to establish social rank and affect mating success. Population density, combined with anthropogenic effects such as harvest, is thought to influence antler size. Antler size increased as densities of moose decreased, ostensibly a density-dependent response related to enhanced nutrition at low densities. The vegetation type where moose were harvested also affected antler size, with the largest-antlered males occupying more open habitats. Hunts with guides occurred in areas with low moose density, minimized hunter interference and increased rates of success. Such hunts harvested moose with larger antler spreads than did non-guided hunts. Knowledge and abilities allowed guides to satisfy demands of trophy hunters, who are an integral part of the Alaskan economy. Heavy harvest by humans was also associated with decreased antler size of moose, probably via a downward shift in the age structure of the population resulting in younger males with smaller antlers. Nevertheless, density-dependence was more influential than effects of harvest on age structure in determining antler size of male moose. Indeed, antlers are likely under strong sexual selection, but we demonstrate that resource availability influenced the distribution of these sexually selected characters across the landscape. We argue that understanding population density in relation to carrying capacity (K) and the age structure of males is necessary to interpret potential consequences of harvest on the genetics of moose and other large herbivores. Our results provide researchers and managers with a better understanding of variables that affect the physical condition, antler size, and perhaps the genetic composition of populations, which may be useful in managing and modelling moose populations.
A database of approximately 9000 trophy measurements of ungulates hunted in South Africa between 1993 and 2001 was analysed in order to detect monotonic trends in trophy quality over time. In a species-specific analysis, declines were found for impala (Aepyceros melampus), springbok (Antidorcas marsupialis) and mountain reedbuck (Redunca fulvorufula). In an area-specific analysis, a decline was found in the Northern Cape Province. Conversely, blesbok (Damaliscus dorcas phillipsi) (species-specific) and the Free State Province (area-specific) showed increases in trophy quality. As an economic indicator, the monitoring of trophy quality allows agencies to potentially evaluate the quality and sustainability of their 'huntable' ungulate resources.
This paper presents the relationships and development of forestry and wildlife management in Hungary during the past 70 years. Current problems of coordination are rooted in the cardinal principle of Hungarian forestry that defines the purpose of forest management as "sustainable and increasing wood production", and regards recreational, educational, and wildlife management as secondary uses. Forestry and game management share several common elements such as educational and scientific underpinnings, direction and regulation, and planning systems. Nonetheless, poor coordination and profit-driven management have resulted in serious resource conflicts associated with extensive clearcutting, habitat destruction, diminished diversity in tree plantations, game damage to reforestation efforts, and other problems. Scientific and professional cooperation are necessary to create an ecologically-sound basis to coordinate resource uses and to harmonize the objectives of timber production, nature protection, and wildlife management in Hungarian forests.
Summary 1. Ecologically significant evolutionary change, occurring over tens of generations or fewer, is now widely documented in nature. These findings counter the long-standing assumption that ecological and evolutionary processes occur on different time-scales, and thus that the study of ecological processes can safely assume evolutionary stasis. Recognition that substantial evolution occurs on ecological time-scales dissolves this dichotomy and provides new opportunities for integrative approaches to pressing ques- tions in many fields of biology. 2. The goals of this special feature are twofold: to consider the factors that influence evolution on ecological time-scales - phenotypic plasticity, maternal effects, sexual selection, and gene flow - and to assess the consequences of such evolution - for population persistence, speciation, community dynamics, and ecosystem function. 3. The role of evolution in ecological processes is expected to be largest for traits that change most quickly and for traits that most strongly influence ecological interactions. Understanding this fine-scale interplay of ecological and evolutionary factors will require a new class of eco-evolutionary dynamic modelling. 4. Contemporary evolution occurs in a wide diversity of ecological contexts, but appears to be especially common in response to anthropogenic changes in selection and population structure. Evolutionary biology may thus offer substantial insight to many conservation issues arising from global change. 5. Recent studies suggest that fluctuating selection and associated periods of contemporary evolution are the norm rather than exception throughout the history of life on earth. The consequences of contemporary evolution for population dynamics and ecological interactions are likely ubiquitous in time and space.
Hunting can affect animal populations not only by increasing mortality but also by introducing selection components associated
with particular features of individuals. In addition to the most widespread hunting system in Spain for Iberian red deer stags
(Cervus elaphus hispanicus) called montería, there are also selective monterías aimed at culling poor-trophy males in order to improve the average quality
of the trophies for commercial hunt. This way of removing poor-trophy males contrasts with the most common procedure of shooting
individual males by selective stalking that is used in other areas of Europe. Also, due to the hunting procedure by which
most deer are shot while running chased by dogs, it is doubtful whether hunters are actually producing a selective impact
on deer populations. In this paper, we compare data of males shot in commercial montería and in selective montería in Southern
Spain. We found that males in selective montería were smaller in body size and in antler size than in commercial hunts, even
correcting by age, although the selective effect was stronger at some ages. We discuss the implications of this practice for
sustainable use and conservation.
Given that the introduction of allochthonous deer breeds in Spanish farms and hunting estates is becoming increasingly common, it is urgent to describe the morphology of Iberian red deer (Cervus elaphus hispanicus) antlers. We use over 2,000 cast antlers collected in Sierra Morena (southern Spain) to provide reference values for beam and first (brow) tine length, beam and burr circumference, and antler weight, depending on the number of antler points. In addition, this study includes a mean gross score of the trophy calculated according to the official formulae, as well as its correlation with the antler variables considered in this study. Beam length is the single most important factor for high score trophies, while factors such as antler weight or the number of antler points contribute little to the gross score. Management implications of these data are discussed.
The dynamics of ungulate populations depend not only on the size, but also on the sex- and age-structure of the population. Successful management therefore depends on obtaining estimates of the age composition. Variation in performance due to age can be fairly well described by stages, and simple, rough methods for ageing cervids can therefore be useful to management. We assessed the performance of three relatively simple and objective methods based on tooth wear (height of molar), weight of eye lenses and diameter of pedicles (males only) on a sample of 77 female and 81 male European roe deer Capreolus capreolus from Lier, Norway. The relationship between tooth wear and age was linear, whereas the relationship between weight of eye lenses and diameter of pedicles was curvilinear with age, likely making them unreliable for old age classes. However, as only three males and six females ≥ 6 years old were included, we were unable to assess the uncertainty in age estimation for older age classes precisely. No simple method could precisely age roe deer, even up to five years of age. Our results do suggest that tooth wear, i.e. height of molar, can serve as a very simple and objective measure of age in roe deer, given that moderate precision (an error rate of ± 1 year and a success rate of 70% up to four years of age) is sufficient to reach management aims. As residuals between age estimates based on tooth wear and diameter of pedicle were not correlated, combining these methods improved the fit slightly. Since tooth wear may differ between areas, the scales presented here may perform less well in other areas, and a calibration for each area is clearly recommended.
Human harvests can select against phenotypes favoured by natural selection, and natural resource managers should evaluate possible artificial selection on wild populations. Because the required genetic data are extremely difficult to gather, however, managers typically rely on harvested animals to document temporal trends. It is usually unknown whether these data are unbiased. We explore our ability to detect a decline in horn size of bighorn sheep (Ovis canadensis) by comparing harvested males with all males in a population where evolutionary changes owing to trophy hunting were previously reported. Hunting records underestimated the temporal decline, partly because of an increasing proportion of rams that could not be harvested because their horns were smaller than the threshold set by hunting regulations. If harvests are selective, temporal trends measured from harvest records will underestimate the magnitude of changes in wild populations.
Advances in ecological science and increasing public environmental awareness have resulted in changes in the management of renewable natural resources. To achieve sustainable use of wildlife, managers need reliable data on populations, habitats, and the complexities of ecological interactions. The National Game Management Database (NGMD) was first mandated by the Hungarian Game Management and Hunting Law in 1996. In this paper, the authors summarize the origins, characteristics, development, and results leading to the final establishment of and uses for the NGMD. Goals of the NGMD are to store data on game populations and game management, provide input to spatial analyses and mapping, and to facilitate decision-making and planning efforts of game management administration. It contains information on the populations of game species, data from annual game management reports, trophy-scoring data, maximum allowed and minimum huntable population size, and maps and long-term game management plans for each GMU and the 24 game management regions. In Hungary, the NGMD was the first operating database in wildlife management and nature conservation providing full GIS capabilities, supporting geographical analyses.
Human harvest of phenotypically desirable animals from wild populations imposes selection that can reduce the frequencies of those desirable phenotypes. Hunting and fishing contrast with agricultural and aquacultural practices in which the most desirable animals are typically bred with the specific goal of increasing the frequency of desirable phenotypes. We consider the potential effects of harvest on the genetics and sustainability of wild populations. We also consider how harvesting could affect the mating system and thereby modify sexual selection in a way that might affect recruitment. Determining whether phenotypic changes in harvested populations are due to evolution, rather than phenotypic plasticity or environmental variation, has been problematic. Nevertheless, it is likely that some undesirable changes observed over time in exploited populations (e.g., reduced body size, earlier sexual maturity, reduced antler size, etc.) are due to selection against desirable phenotypes-a process we call "unnatural" selection. Evolution brought about by human harvest might greatly increase the time required for over-harvested populations to recover once harvest is curtailed because harvesting often creates strong selection differentials, whereas curtailing harvest will often result in less intense selection in the opposing direction. We strongly encourage those responsible for managing harvested wild populations to take into account possible selective effects of harvest management and to implement monitoring programs to detect exploitation-induced selection before it seriously impacts viability.
We explore variation in the prices paid by recreational hunters of trophy animals in Africa and its possible causes, including perceived rarity. Previous work has raised the possibility that extinction can result if demand rises fast enough as a species becomes rarer. We attempt to disentangle this from other inter-correlated influences affecting price. Species with larger body sizes and larger trophies were more valuable. Value increased less steeply as a function of size for bovids than for felids and the effect was consistent across countries. Power laws, ubiquitous in physical and social systems, described the trends. The exponent was approximately 0.4 for bovids, compared with approximately 1.0 for felids. Rarity (as indexed by IUCN score) influenced the value of bovid trophies - price was higher for species in categories denoting higher global threat. There was substantial variation in price among and within families not explained by either size or rarity. This may be attributable to a 'charisma' effect, which seems likely to be a general attribute of human perceptions of wildlife. Species where prices were higher than predicted by size or rarity are ranked high in published accounts of desirability by hunters. We conclude that the valuation of these species is explicable to a large extent by body size and perceived rarity, and that differences in valuation between taxonomic groups are related to less easily quantified 'charisma' effects. These findings are relevant for conservationists considering the threat status of species exploited in open access markets, and where license quotas are adjusted in response to changes in perceived rarity.
Structured additive regression models are perhaps the most commonly used class of models in statistical applications. It includes, among others, (generalized) linear models, (generalized) additive models, smoothing spline models, state space models, semiparametric regression, spatial and spatiotemporal models, log-Gaussian Cox processes and geostatistical and geoadditive models. We consider approximate Bayesian inference in a popular subset of structured additive regression models, "latent Gaussian models", where the latent field is Gaussian, controlled by a few hyperparameters and with non-Gaussian response variables. The posterior marginals are not available in closed form owing to the non-Gaussian response variables. For such models, Markov chain Monte Carlo methods can be implemented, but they are not without problems, in terms of both convergence and computational time. In some practical applications, the extent of these problems is such that Markov chain Monte Carlo sampling is simply not an appropriate tool for routine analysis. We show that, by using an integrated nested Laplace approximation and its simplified version, we can directly compute very accurate approximations to the posterior marginals. The main benefit of these approximations is computational: where Markov chain Monte Carlo algorithms need hours or days to run, our approximations provide more precise estimates in seconds or minutes. Another advantage with our approach is its generality, which makes it possible to perform Bayesian analysis in an automatic, streamlined way, and to compute model comparison criteria and various predictive measures so that models can be compared and the model under study can be challenged. Copyright (c) 2009 Royal Statistical Society.
There is growing concern about the evolutionary consequences of human harvesting on phenotypic trait quality in wild populations. Undesirable consequences are especially likely with trophy hunting because of its strong bias for specific phenotypic trait values, such as large antlers in cervids and horns in bovids. Selective hunting can cause a decline in a trophy trait over time if it is heritable, thereby reducing the long-term sustainability of the activity itself.
How can we build a sustainable trophy hunting tradition without the negative trait-altering effects? We used an individual-based model to explore whether selective compensatory culling of ‘low quality’ individuals at an early life stage can facilitate sustainability, as suggested by information from managed game populations in eastern and central Europe. Our model was rooted in empirical data on red deer, where heritability of sexual ornaments has been confirmed and phenotypic quality can be assessed by antler size in individuals as young as 1 year.
Simulations showed that targeted culling of low-quality yearlings could counter the selective effects of trophy hunting on the distribution of the affected trait (e.g. antler or horn size) in prime-aged individuals. Assumptions of trait heritability and young-to-adult correlation were essential for compensation, but the model proved robust to various other assumptions and changes to input parameters. The simulation approach allowed us to verify responses as evolutionary changes in trait values rather than short-term consequences of altered age structure, density and viability selection.
We conclude that evolutionarily enlightened management may accommodate trophy hunting. This has far reaching implications as income from trophy hunting is often channelled into local conservation efforts and rural economies. As an essential follow-up, we recommend an analysis of the effects of trophy hunting in conjunction with compensatory culling on the phenotypic and underlying genetic variance of the trophy trait.
The observable traits of wild populations are continually shaped and reshaped by the environment and numerous agents of natural selection, including predators. In stark contrast with most predators, humans now typically exploit high proportions of prey populations and target large, reproductive-aged adults. Consequently, organisms subject to consistent and strong 'harvest selection' by fishers, hunters, and plant harvesters may be expected to show particularly rapid and dramatic changes in phenotype. However, a comparison of the rate at which phenotypic changes in exploited taxa occurs relative to other systems has never been undertaken. Here, we show that average phenotypic changes in 40 human-harvested systems are much more rapid than changes reported in studies examining not only natural (n = 20 systems) but also other human-driven (n = 25 systems) perturbations in the wild, outpacing them by >300% and 50%, respectively. Accordingly, harvested organisms show some of the most abrupt trait changes ever observed in wild populations, providing a new appreciation for how fast phenotypes are capable of changing. These changes, which include average declines of almost 20% in size-related traits and shifts in life history traits of nearly 25%, are most rapid in commercially exploited systems and, thus, have profound conservation and economic implications. Specifically, the widespread potential for transitively rapid and large effects on size- or life history-mediated ecological dynamics might imperil populations, industries, and ecosystems.
Overexploitation and subsequent collapse of marine fishes has focused attention on the ability of affected populations to recover to former abundance levels and on the degree to which their persistence is threatened by extinction. Although potential for recovery has been assessed indirectly, actual changes in population size following long-term declines have not been examined empirically. Here I show that there is very little evidence for rapid recovery from prolonged declines, in contrast to the perception that marine fishes are highly resilient to large population reductions. With the possible exception of herring and related species that mature early in life and are fished with highly selective equipment, my analysis of 90 stocks reveals that many gadids (for example, cod, haddock) and other non-clupeids (for example, flatfishes) have experienced little, if any, recovery as much as 15 years after 45-99% reductions in reproductive biomass. Although the effects of overfishing on single species may generally be reversible, the actual time required for recovery appears to be considerable. To exempt marine fishes from existing criteria used to assign extinction risk would be inconsistent with precautionary approaches to fisheries management and the conservation of marine biodiversity.
"As a cohort of people, animals, or machines ages, the individuals at highest risk tend to die or exit first. This differential selection can produce patterns of mortality for the population as a whole that are surprisingly different from the patterns for subpopulations or individuals. Naive acceptance of observed population patterns may lead to erroneous policy recommendations if an intervention depends on the response of individuals. Furthermore, because patterns at the individual level may be simpler than composite population patterns, both theoretical and empirical research may be unnecessarily complicated by failure to recognize the effects of heterogeneity."
Phenotype-based selective harvests, including trophy hunting, can have important implications for sustainable wildlife management if they target heritable traits. Here we show that in an evolutionary response to sport hunting of bighorn trophy rams (Ovis canadensis) body weight and horn size have declined significantly over time. We used quantitative genetic analyses, based on a partly genetically reconstructed pedigree from a 30-year study of a wild population in which trophy hunting targeted rams with rapidly growing horns, to explore the evolutionary response to hunter selection on ram weight and horn size. Both traits were highly heritable, and trophy-harvested rams were of significantly higher genetic 'breeding value' for weight and horn size than rams that were not harvested. Rams of high breeding value were also shot at an early age, and thus did not achieve high reproductive success. Declines in mean breeding values for weight and horn size therefore occurred in response to unrestricted trophy hunting, resulting in the production of smaller-horned, lighter rams, and fewer trophies.
Harvesting represents a major source of mortality in many deer populations. The extent to which harvesting is selective for specific traits is important in order to understand contemporary evolutionary processes. In addition, since such data are frequently used in life-history studies, it is important to know the pattern of selectivity as a source of bias. Recently, it was demonstrated that different hunting methods were selected for different weights in red deer (Cervus elaphus), but little insight was offered into why this occurs. In this study, we show that foreign trophy stalkers select for larger antlers when hunting roe deer (Capreolus capreolus) than local hunters, but that close to half of the difference in selectivity was due to foreigners hunting earlier in the season and in locations with larger males. The relationship between antler size and age was nevertheless fairly similar based on whether deer was shot by foreign or local hunters.
Much insight can be derived from records of shot animals. Most researchers using such data assume that their data represents a random sample of a particular demographic class. However, hunters typically select a non-random subset of the population and hunting is, therefore, not a random process. Here, with red deer (Cervus elaphus) hunting data from a ranch in Toledo, Spain, we demonstrate that data collection methods have a significant influence upon the apparent relationship between age and weight. We argue that a failure to correct for such methodological bias may have significant consequences for the interpretation of analyses involving weight or correlated traits such as breeding success, and urge researchers to explore methods to identify and correct for such bias in their data.
Many collapsed fish populations have failed to recover after a decade or more with little fishing. This may reflect evolutionary change in response to the highly selective mortality imposed by fisheries. Recent experimental work has demonstrated a rapid genetic change in growth rate in response to size-selective harvesting of laboratory fish populations. Here, we use a 30-year time-series of back-calculated lengths-at-age to test for a genetic response to size-selective mortality in the wild in a heavily exploited population of Atlantic cod (Gadus morhua). Controlling for the effects of density- and temperature-dependent growth, the change in mean length of 4-year-old cod between offspring and their parental cohorts was positively correlated with the estimated selection differential experienced by the parental cohorts between this age and spawning. This result supports the hypothesis that there have been genetic changes in growth in this population in response to size-selective fishing. Such changes may account for the continued small size-at-age in this population despite good conditions for growth and little fishing for over a decade. This study highlights the need for management regimes that take into account the evolutionary consequences of fishing.
The first edition of this book has established itself as one of the leading references on generalized additive models (GAMs), and the only book on the topic to be introductory in nature with a wealth of practical examples and software implementation. It is self-contained, providing the necessary background in linear models, linear mixed models, and generalized linear models (GLMs), before presenting a balanced treatment of the theory and applications of GAMs and related models. The author bases his approach on a framework of penalized regression splines, and while firmly focused on the practical aspects of GAMs, discussions include fairly full explanations of the theory underlying the methods. Use of R software helps explain the theory and illustrates the practical application of the methodology. Each chapter contains an extensive set of exercises, with solutions in an appendix or in the book’s R data package gamair, to enable use as a course text or for self-study.
In a 1935 paper and in his book Theory of Probability, Jeffreys developed a methodology for quantifying the evidence in favor of a scientific theory. The centerpiece was a number, now called the Bayes factor, which is the posterior odds of the null hypothesis when the prior probability on the null is one-half. Although there has been much discussion of Bayesian hypothesis testing in the context of criticism of P-values, less attention has been given to the Bayes factor as a practical tool of applied statistics. In this article we review and discuss the uses of Bayes factors in the context of five scientific applications in genetics, sports, ecology, sociology, and psychology. We emphasize the following points:
We review the impact of developments from animal breeding on our understanding of evolution and on the methodology used in evolutionary biology. The theory developed for improvement of polygenic traits, in particular the breeders' equation and the effects of finite population size, has had a significant influence. The effectiveness of within population selection is exemplified by the continued rapid genetic change, often with concomitant effects on fitness, produced by breeders. Many of the models and methods for estimation of quantitative genetic parameters, notably the animal model, have been motivated by animal breeding problems. Results from selection programs and quantitative trait loci (QTL) experiments show quantitative traits are often highly polygenic and can be adequately modeled by the infinitesimal model.