Article

Age and season determine European rabbit habitat use in Mediterranean ecosystems

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Knowledge about the factors determining habitat use is especially interesting for herbivores living under seasonal climates as they have to deal with food shortage during the drought season. In this context, different-aged individuals are expected to respond differently to seasonal variations because nutritional requirements and predation risk can vary with age. We investigated adult and juvenile European rabbit (Oryctolagus cuniculus) habitat use in a Mediterranean ecosystem of central Spain, during spring, summer and winter. Relationships between adult and juvenile rabbit pellet abundances and 11 environmental variables related to food availability and refuge density were analysed by means of multiple regression, and evaluated using information theory to identify the set of models best supported by the data. Density of warren entrances was the more constant predictor of habitat use for juvenile rabbits in all the seasons. Herbaceous vegetation volume had a negative influence and was the strongest predictor for adult rabbit habitat use in spring and winter. In summer, green vegetation cover became the strongest positive habitat use predictor. These results suggest that adults prefer to forage in low volume swards ensuring a wide sensory range for the detection of approaching predators. However, the arrival of summer and its associated food depletion forces them to shift toward more open productive areas where green vegetation persists, but at the expense of higher predation risk. Seasonal variation induces minor changes in juvenile habitat use due to their strong dependence on warrens. Thus, our results show that rabbit habitat use is influenced by animal age and seasonal variations in resources.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Por lo anterior, el objetivo de este estudio fue determinar la época reproductiva de S. floridanus dentro de un ecosistema árido de la Ciudad de México, a partir del análisis de la abundancia y tamaño de sus heces. Se espera que durante la temporada de lluvias, cuando hay una mayor disponibilidad de recursos alimentarios (Cano-Santana, 1994b), haya un incremento en la frecuencia en la que se detecten heces de pequeño tamaño pertenecientes a individuos jóvenes (Rueda et al., 2008), tal como lo encontraron Cervantes y Vázquez (2008) en Ixtacuixtla, Tlaxcala. ...
... Se llevaron a cabo 2 periodos de muestreo de la abundancia de heces con un método parecido al que aplicaron Rueda et al. (2008). En un primer periodo se seleccionaron 24 cuadros permanentes de 50 × 50 cm distribuidos equitativamente en 4 parcelas de 10 × 10 m dentro de la zona núcleo poniente separadas entre sí por al menos 50 m localizadas en áreas que mantenían una alta actividad y abundancia de conejos, según datos de Dorantes-Villalobos (2017). ...
... En este muestreo, las heces colectadas en la última semana de cada mes, entre agosto y mayo, fueron llevadas al laboratorio para medir su longitud. Esto con el fin de detectar cómo cambia la frecuencia de heces de distinto tamaño a lo largo del año, considerando que el tamaño de las heces está directamente relacionado con la talla del conejo, de modo que los juveniles depositarían las excretas más pequeñas (Rueda et al., 2008;Simonetti y Fuentes, 1982). Para probar si el periodo reproductivo (ésto es, la temporada de mayor abundancia de heces) se mantenía constante a través de los años, se llevó a cabo un segundo periodo de muestreo de 3 años consecutivos, en el cual se contaron mensualmente, de noviembre de 2016 a mayo de 2019, las heces en 10 cuadros permanentes del mismo tamaño, distribuidas en un área de 70 × 70 m con alta actividad y abundancia de conejos castellanos dentro de la zona núcleo poniente. ...
Article
Full-text available
Reproduction requires large amounts of energy, so many organisms look for the ideal season to carry out this process. For example, each population of the Eastern Cottontail, Sylvilagus floridanus, is expected to adjust its life cycle to reproduce in the most suitable season of the year, which may vary depending on the particular conditions of the site where each one lives. The objective of this study was to determine at what time of the year this rabbit reproduces in the xerophilous scrub of the Pedregal of San Ángel, México City, based on an analysis of seasonal variation of the abundance and size of its feces. Monthly systematic sampling of abundance of feces was made at established sites for 4 years and, during the first year, the size of excreta was also recorded. Data was analyzed using a χ2 test. It was recorded that small fecal pellets are concentrated in September and that the highest abundance values were recorded between October and December. The data suggest that the reproductive period occurs in August, which is a month of greater food availability. The data obtained do not coincide with the reproductive season recorded by this species in other locations.
... In Rueda et al. [Rueda, M., Rebollo, S., Gá lvez-Bravo, L., 2008. Age and season determine European rabbit habitat use in Mediterranean ecosystems. ...
... In our original study (Rueda et al., 2008), we used a threshold of 6 mm pellet diameter to differentiate between adult and juvenile European rabbits in order to assess habitat use in three seasons, spring, summer and winter, and five large-scale habitat classes. After independently relating adult and juvenile rabbit pellet abundances with 11 environmental variables associated to food and refuge, we found that seasonal variation in resources induced small changes in juvenile rabbit habitat use due to their strong dependence on warrens as refuge. ...
... Delibes-Mateos et al. found that their 12 adult rabbits produced the same total number of >6 mm diameter pellets in 10 days as <6 mm pellets. These authors criticise the threshold used by Rueda et al. (2008) and consider that these findings demonstrate that pellet size is an unsuitable method for aging wild rabbits in the field. In response to Delibes-Mateos et al. we would like to point out the following: ...
... Similarly, Bhadresa (1982) suggested that pellet weight might be used in New Zealand white rabbits to determine rabbit age. Rueda (2006), Dellafiore (2007) and Rueda et al. (2008) subsequently used a method based on pellet size to differentiate adult and juvenile rabbits. These authors considered that pellets >6 mm in diameter were deposited by adults, while those <6 mm in diameter were deposited by juveniles or kittens. ...
... The pellets collected at each station were stored in separate labeled paper bags, and sorted using 4 mm and 6 mm diameter sieves. The proportions of pellets >6 mm diameter and >4 mm diameter were calculated for comparison with the proportion of adults and juveniles in the populations, according to the method of Rueda et al. (2008). ...
... Surprisingly, there was no common pattern among populations; in some cases the estimates of the proportion of adults based on pellet size were underestimates, and in others overestimates. Even though if the proportion of pellets <6 mm diameter was similar to the proportion of captured juveniles this would not mean that the pellets <6 mm diameter could be assigned to juveniles or vice versa (e.g. to analyze habitat use; Rueda et al., 2008). It may occur, for example, that some adults mainly produce small pellets, as showed by Delibes-Mateos et al. (2009), while some juveniles deposit large pellets, hence balancing in the population the overall proportion of pellets >6 mm in diameter. ...
Article
Techniques for estimating the age of wild animals are crucial to many aspects of the study of population biology. Accurate estimates of the proportion of different age classes in wild rabbit populations would be very useful, and the possibility that it could be obtained from the pellet size holds great appeal. However, this suggestion has created controversy in the literature as this technique has not been validated. This study involved assessment of whether threshold fecal pellet diameters could be used to differentiate adult and juvenile rabbits. The proportion of adults in four wild rabbit populations living in semi-natural conditions was compared with the proportion of animal pellets greater than threshold diameters of 6 mm and 4 mm. Our results suggest that inferring a relationship between the proportion of pellets >6 mm diameter and the proportion of adults in a population is not applicable to European wild rabbits, and that the use of this method could produce erroneous interpretations. The use of a 4 mm pellet diameter threshold appeared to produce even more inaccurate results. Studies that use this technique should include validation, as the results can vary greatly among individuals and populations.
... Recently, Rueda et al. (2008) developed a new methodology to differentiate between juvenile and adult rabbits based on faecal pellet size. According to their method, pellets >6 mm in diameter are inferred to be deposited by adults, while those <6 mm are inferred to be deposited by juveniles or kittens. ...
... According to their method, pellets >6 mm in diameter are inferred to be deposited by adults, while those <6 mm are inferred to be deposited by juveniles or kittens. Given that their method has not been validated, we designed a simple experiment to test the assumptions made by Rueda et al. (2008). In this study, we tested whether adult rabbits produce predominantly large pellets (>6 mm diameter) or whether they are also able to deposit a high proportion of smaller pellets (<6 mm diameter). ...
... In contrast to the assumption of Rueda et al. (2008), we observed that adult rabbits frequently produce pellets <6 mm diameter (Fig. 1), and we found no significant difference between the number of small (n ¼ 23,613) and large (n ¼ 23,457) pellets in the experiment (F 1,238 ¼ 0.005; p ¼ 0.93). Our findings suggest that Rueda et al.'s (2008) methodology for differentiating adults from juveniles on the basis of pellet size is likely to significantly over-estimate the number of juvenile rabbits in an area. ...
Article
Recently, a new method for differentiating juvenile and adult rabbits based on faecal pellet size was published. According to this method, pellets >6 mm diameter are inferred to be deposited by adults, while those <6 mm are inferred to be from juveniles or kittens. In this study, we designed a simple experiment to test the accuracy of this methodology. Twelve adult rabbits were housed in individual outdoor cages and their pellets were removed every day for 10 consecutive days. Pellets were separated using a sieve according to their size and counted. Results showed that adult rabbits produce pellets >6 mm diameter in the same proportion as those <6 mm. We also observed a strong influence of the individual rabbit on pellet size; some rabbits produce a high proportion of pellets >6 mm, whereas others deposit mostly pellets <6 mm in size. Our findings demonstrate that pellet size is unsuitable for aging wild rabbits. Field biologists should therefore be cautious when employing the pellet size method of age determination in other wild animals in the absence of validating studies.
... Based on tooth eruption and epiphyseal fusion of the humerus, femur and tibia (Jones, 2006), there are no individuals below the age of two months and few between the age of two and 10 months in the assemblage. The proportion of adults on the Iberian landscape is greatest during autumn, with young juveniles being most prominent during spring (Rueda et al., 2008). This is because although the European rabbit is able to produce young year-round in southern Iberia, rabbit births peak during March and April (Rogers and Myers, 1979; Gonçalves et al., 2002). ...
... This is because although the European rabbit is able to produce young year-round in southern Iberia, rabbit births peak during March and April (Rogers and Myers, 1979; Gonçalves et al., 2002). Breeding is dictated by climate, since both temperature and precipitation affect the availability of vegetation and water, which in turn influences rabbit reproduction as well as the occurrence and visibility of adults on the landscape (Gonçalves et al., 2002; Rueda et al., 2008). Rabbits prefer to remain on the boundaries between vegetation zones and thus are well-adapted to the patchy Iberian landscape (Rogers and Myers, 1979; Rueda et al., 2008). ...
... Breeding is dictated by climate, since both temperature and precipitation affect the availability of vegetation and water, which in turn influences rabbit reproduction as well as the occurrence and visibility of adults on the landscape (Gonçalves et al., 2002; Rueda et al., 2008). Rabbits prefer to remain on the boundaries between vegetation zones and thus are well-adapted to the patchy Iberian landscape (Rogers and Myers, 1979; Rueda et al., 2008). During the spring, when vegetation biomass is high and green vegetation is readily available, both adults and juveniles tend to stay close to their warrens (Rueda et al., 2008 ). ...
Article
This paper will focus on the ecology of the first Anatomically Modern Humans in SW Iberia based on the rock shelter of Vale Boi (Algarve, Portugal), a site with a long stratigraphic record starting with Late Middle Paleolithic followed by early Gravettian, Proto-Solutrean, Solutrean, and Magdalenian. Early Gravettian remains are present in various areas and different levels of the site, and are dated to c. 32 ka cal BP, corresponding to the earliest modern human occupation in SW Iberia. These communities most likely came from the Iberian Mediterranean coast as bone technology and body ornaments seem to confirm. The Gravettian of Vale Boi provides clear evidence of an intensification and diversification of dietary resources from very early, including the use of grease-rendering. Here, reconstruction of the Gravettian human ecology at Vale Boi is based on the diversity of human occupations, focusing mostly on diachronic changes in the patterns of resources acquisition and land-use, but also on subsistence, technological, social and symbolic elements.
... This could be related to the fact that higher soil moisture at lowlands limits rabbit burrowing. As a central-place forager, the scarcity of burrows constrains rabbit access to the high-productivity sites (Rueda et al. 2008). Furthermore, rabbits usually show a strong preference for shorter swards, where they can spend more time foraging and less time scanning for predators (Iason et al. 2002). ...
... Furthermore, rabbits usually show a strong preference for shorter swards, where they can spend more time foraging and less time scanning for predators (Iason et al. 2002). We have evidence (dropping counts, see also Rueda et al. 2008) that except in spring, when the vegetation is tallest, rabbits used the large plus small herbivore plots in lowlands, suggesting that sheep grazing/ trampling might facilitate rabbit access to these plots, as has been demonstrated in other studies (Bakker et al. 2009;Denyer et al. 2010). ...
Article
Vertebrate herbivores can be key determinants of grassland plant species richness, although the magnitude of their effects can largely depend on ecosystem and herbivore characteristics. It has been demonstrated that the combined effect of primary productivity and body size is critical when assessing the impact of herbivores on plant richness of perennial-dominated grasslands; however, the interaction of site productivity and herbivore size as determinants of plant richness in annual-dominated pastures remains unknown. We experimentally partitioned primary productivity and herbivore body size (sheep and wild rabbits) to study the effect of herbivores on the plant species richness of a Mediterranean semiarid annual plant community in central Spain over six years. We also analyzed the effect of grazing and productivity on the evenness and species composition of the plant community, and green cover, litter, and plant height. We found that plant richness was higher where the large herbivore was present at high-productivity sites but barely changed at low productivity. The small herbivore did not affect species richness at either productivity site despite its large effects on species composition. We propose that adaptations to resource scarcity and herbivory prevented plant richness changes at low-productivity sites, whereas litter accumulation in the absence of herbivores decreased plant richness at high productivity. Our results are consistent with predictions arising from a long history of grazing and highlight the importance of both large and small herbivores to the maintenance of plant diversity of Mediterranean annual-dominated pastures.
... On the Iberian Peninsula, the rabbit has a wide distribution and it has been observed in diverse ecosystems, from Mediterranean scrublands to dehesa agroecosystems, mountainous areas, and coastal sand dunes (e.g. Rueda et al., 2008aRueda et al., , 2008bBarrio et al., 2009;Dellafiore et al., 2009;Tapia et al., 2010Tapia et al., , 2014. The coastal sand dune ecosystem represents 40% of the 7,880 km of the Iberian coast (Ley et al., 2011) and rabbit populations have been observed in almost all such sand dune areas (Villafuerte, 2002), but they have been poorly studied to date. ...
... Other authors found seasonal differences in habitat use by rabbits in grassland environments (Rueda García, 2006;Rueda et al., 2008aRueda et al., , 2008b. In our study area, although we did not test for differences in habitat use between seasons, we found no change in habitat use in each season. ...
Article
Full-text available
We studied habitat use by the wild European rabbit (Oryctolagus cuniculus) in a coastal sand dune system in the south western Iberian peninsula. Our goals were to define the use of this habitat by rabbits in relation to food and shelter availability between seasons. Rabbit density, food availability and refuge abundance were analysed using multiple regression analyses. We found that, independently of season, habitat selection was principally related to cover by the woody shrub Retama monosperma which rabbits use both as a food resource and as protection against predators. Although it is an invasive native plant, the benefits that R. monosperma provides to the wild rabbit population should be taken into account when deciding wild rabbit management strategies.
... Alternative methods for estimating rabbit (multiple species) population densities include warren counts (Palomares 2001;Rueda et al. 2008), pellet counts (Palomares 2001;Rueda et al. 2008), line transects (Palomares 2001) and counts of individuals, including roadside counts (Woolf et al. 1993) and spotlight counts (Barrio et al. 2010a). Warren counts are not possible for eastern cottontail rabbits because they do not dig burrows (Schwartz et al. 2002) and pellet counts are unreliable (Palomares 2001). ...
... Alternative methods for estimating rabbit (multiple species) population densities include warren counts (Palomares 2001;Rueda et al. 2008), pellet counts (Palomares 2001;Rueda et al. 2008), line transects (Palomares 2001) and counts of individuals, including roadside counts (Woolf et al. 1993) and spotlight counts (Barrio et al. 2010a). Warren counts are not possible for eastern cottontail rabbits because they do not dig burrows (Schwartz et al. 2002) and pellet counts are unreliable (Palomares 2001). ...
Article
Full-text available
Eastern cottontail rabbits (Sylvilagus floridanus) are common, conspicuous denizens of urban environments. They are associated with human-wildlife conflict due to vegetation damage. Prior to this study, population dynamics of this species in urban environments remained largely uncharacterized. For three consecutive winters, we used classic field ecology methods (mark-recapture and mark–resight surveys) to estimate demographic parameters of rabbits in a city park in Chicago, Illinois. Rabbits occurred in densities as high as 16.3 rabbits/ha, which is comparatively high for the Midwestern United States. An annual survivorship of 30.4 ± 12.9 % SE was similar to that observed in natural environments in similar climates. This result refuted our hypothesis that urban rabbits would have higher annual survival rates than rabbits in natural settings due to food subsidies supplied by landscaping in parks. Mean distance between trap locations for rabbits trapped three or more times was 43.14 ± 30.01 m SD, suggesting that rabbits in the urban study area had smaller home ranges than rabbits in non-human-dominated habitats. This study contributes to our understanding of population dynamics of a human-wildlife conflict species in urban environments and provides useful information for managers dealing with damage caused by rabbits. The mark-resight method employed here could be used by managers to estimate pre- and post-management population sizes of other conflict species, for example Canada geese (Branta Canadensis), in parks and green spaces, provided that the species is trappable, visible, and individuals have relatively small home ranges.
... Plant phenology may partially explain the strong seasonal variations on rabbit distribution. In fact, wild rabbit strategies of using space depend on the availability of different plant species and on their actual nutritive value (Soriguer 1988; Rueda et al. 2008; Ferreira and Alves 2009). And, wild rabbit reproductive phenology, which is clearly influenced by plant phenology (Gonçalves et al. 2002; Martins et al. 2002), also seems to play an important role on seasonal changes in distribution. ...
Article
Full-text available
Understanding the relationship between spatial patterns of landscape attributes and population presence and abundance is essential for understanding population processes as well as supporting management and conservation strategies. This study evaluates the influence of three factors: environment, habitat management, and season on the presence and abundance of the wild rabbit (Oryctolagus cuniculus), an important prey species for Mediterranean endangered predator species. To address this issue, we estimated wild rabbit presence and abundance by latrine counting in transects located in 45 plots within a 250 × 250 m grid from June 2007 until June 2009 in a 1,200 ha hunting area in southern Portugal. We then analyzed how wild rabbit presence and abundance correlate with the aforementioned factors. Our results showed that the main variable influencing wild rabbit presence and abundance was the distance to the artificial warrens. North and northeast slope directions were negatively related to wild rabbit presence. Conversely, rabbit presence was positively correlated with short distances to ecotone, artificial warrens, and spring. Regarding rabbit abundance, in addition to artificial warrens, soft soils, bushes, and season also had a positive effect. We found that environmental variables, management practices, and season each affect wild rabbit presence and abundance differently at a home range scale in low-density population. Thus, our major recommendations are reducing the distance to artificial warrens and ecotone, ideally to less than 100 m, and promoting habitat quality improvement on slopes with plenty of sun exposure.
... The approximate cover of perennials in uplands and lowlands is 0.25% and 27%, respectively (Rueda, 2006). The dehesa is mainly grazed by a dense native population of wild European rabbits (about 10 warrens/ha) (Rueda et al., 2008) and a transhumant flock of 600 free-ranging sheep (about 2 sheep/ha). Sheep graze from December until the end of June. ...
Article
Herbivores are expected to influence grassland ecosystems by modifying root biomass and root spatial distribution of plant communities. Studies in perennial dominated grasslands suggest that grazing intensity and primary productivity may be strong determinants of the vertical distribution of subterranean biomass. However, no studies have addressed this question in annual dominated pastures. In this study we assess the effect of grazing and habitat productivity on the vertical distribution of root mass in an annual dominated Mediterranean pasture grazed by free-ranging sheep and wild rabbits. We evaluate the effects of grazing on total root mass and vertical root distribution (0-4, 4-8 and 8-12 cm depths) in two neighboring topographic sites (uplands and lowlands) with different productivity using a replicated fence experiment which excludes sheep and sheep plus rabbits. We found evidences that grazing affected root biomass and vertical distribution at lowlands (high productivity habitats), where places grazed by sheep plus rabbits exhibit more root mass and a higher concentration of it towards the soil surface than only rabbits and ungrazed places. In contrast, grazing did not affect root biomass and vertical distribution at uplands (low productivity habitats). We suggest that higher nitrogen and organic matter found in lowlands permit a plant adjustment for nitrogen acquisition by increasing biomass allocation to root production which would allow plant regrowth and the quick completion of the annual life cycle. Contrary, soil resources scarcity at uplands do not permit plants modify their root growth patterns in response to grazing. Our study emphasizes the importance of primary productivity in predicting grazing effect on belowground processes in Mediterranean environments dominated by annuals.
... Estimation of the consumption of forage units (FU) is based on energy needs for maintenance and activity for each animal that comprises the population pyramid. To make this calculation, information about energy needs of each species or for similar species has been used when available (Anderson, 1976;Cassinello, 2003;Cheeke, 1994;Lachica, Nieto, & Aguilera, 2009;Rodríguez-Berrocal, 1993;Rueda, Rebollo, & Gálvez Bravo, 2008;Sahlu et al., 2004). Data about the composition of each population in terms of age and sex (from the population dynamics simulation), and the body weight of specimens according to age and sex has also been used (information from our own fieldwork; Carranza, Alarcos, Sánchez-Prieto, Valencia, & Mateos, 2004;Salvador, 2004). ...
Article
Full-text available
Research has addressed the valuation of hunting and game species according to their extractive value, using both market and non-market methodologies. This study provides a new perspective to estimate environmental prices of game animals based on game hunting leases, population dynamics, the assumption of a steady state, and the use of the residual valuation method. This, in turn, allows the calculation of the contribution of game animal stock to total income from hunting and the value of game animal stock by species, sex, and age. These values are estimated in a manner that is consistent with the exchange value of national accounts, allowing improvement of game species valuation in ecosystem accounting.
... habitat type) rather than structural and functional components. A few examples of some selected landscape variables that were identified in published leporid papers include: edge density, land use (Petrovan et al. 2011), topography, elevation, patch area, distance to roads, orchards, hedges (Roedenbeck and Voser 2008), aspect, altitude (Fulgione 2009), slopes, topography and vegetation (Rueda 2008), soil hardness, vegetation structure, elevation, and scrub height (Calvete 2004). It is important that variables such as altitude, aspect, edge effect, and slope continue to grow within leporid research to obtain a more specific understanding of structure and function of ecological processes in leporid landscapes. ...
Article
Leporids play a dynamic role in the ecosystem and assessments must be undertaken in order to improve research efforts and methods. Landscape ecology metrics are used to quantify components of leporid habitat such as vegetation structure, vegetation cover, habitat type, and fragmentation; however, the degree to which the metrics are utilized in leporid research is relatively unknown. This paper assessed fifty-three published, peer reviewed papers on leporids from various European countries on where the study was done, the species of leporid that was studied, the content of the study (i.e. what the paper focused on), the length of the study, the size of the study area, and the method of study. The quantified landscape metrics within these papers were assessed. This study found that most of the studies occurred in Spain, the European rabbit and European hare were the most studied leporids, many papers were concerned with habitat relationships, many of the studies were conducted in a year or less, many papers utilized pellet surveys and trapping, and the most common landscape metric utilized was habitat type. This survey of research on leporids highlights that there is a lack of utilizing landscape structure and function metrics such as slope, fragmentation, and edge effect. These are important variables to help connect structure and function of ecological processes in the context of leporid habitat and landscapes. It is recommended that leporid researchers and landscape planners exchange research findings so that the best planning practices can occur on the ground for the leporids
... Given such deficiencies in knowledge, assessments of connectivity habitat often rely on expert opinion and simplified assumptions of habitat relationships, including the assumption that habitat use of resident animals is a suitable proxy for dispersal habitat (Harrison 1992;La Rue 2008). However, habitat requirements may be life stage dependent and dispersers may be subject to unique habitat requirements (Beyer et al. 2010;Palomares et al. 1999;Rueda 2008). ...
Thesis
Full-text available
Developing habitat suitability maps of wild animals is essential to generate ecosystem based management plans. Aim of this study was to develop annual and seasonal habitat suitability models and maps based on ecologic, topographic, and anthropogenic variables for the mammalian big wild animals which are brown hare (Lepus capensis L.), wild boar (Sus scrofa L.), badger (Meles meles L.) and beech marten (Martes foina L.) in the Gölcük district. Presence-absence method was used to determine habitat uses and relative habitat uses of the wild animals. Logistic regression analysis and regression tree methods were used as statistical analytical techniques. The validity of the models was confirmed by ten times cross-validation test. The models obtained for each species visualized through the Geographical Information System and in this way, habitat suitability maps achieved on the basis of locality. According to the best models obtained, the efficient habitat variables were young cedar stands, steppe, agricultural fields, meadowlands with little human pressure for the brown hare; forest existence, water sources, soils which can be easily, and meadowlands with little human pressure for the wild boar; meadowlands, proximity to residential areas and water sources, and rocky areas for the badger; and stand gaps, rocky areas, agricultural fields and proximity to residential areas for the marten. While increase in altitude and terrain slope negatively influences the habitat preference of the badger and marten, it positively influences the habitat preference of the wild boar and hare. The hare and wild boar mostly prefer northern aspects, the badger prefers northeastern aspects, and marten prefers southwestern aspects. Keywords: Potential distribution modals, Correlative modals, Mammalian big wild animals 2013, 249 pages Yaban hayvanlarının habitat uygunluk haritalarının yapılması ekosistem tabanlı fonksiyonel planlama için temel teşkil etmektedir. Bu tez çalışmasında, Gölcük yöresinde, ekolojik, topoğrafik ve antropolojik değişkenlerine dayalı olarak memeli büyük yaban hayvanlarından Yaban tavşanı (Lepus capensis L.), Yaban domuzu (Sus scrofa L.), Porsuk (Meles meles L.) ve Kaya sansarı (Martes foina L.) için yıllık ve mevsimsel habitat uygunluk modelleri ve haritalarının elde edilmesi amaçlanmıştır. Var-Yok tarama metodu uygulanarak yaban hayvanlarının habitat kullanımları ve habitat paylaşımları tespit edilmiştir. Analitik istatistiksel yöntem olarak lojistik regresyon ve sınıflandırma ağacı teknikleri kullanılmıştır. Modellerin geçerliliği on kat çapraz doğrulama testiyle teyit edilmiştir. Her tür için elde edilen modeller Coğrafi Bilgi Sistemi aracılığıyla görselleştirilmiş ve böylece türlerin habitat uygunluk haritaları yöre ölçeğinde elde edilmiştir. Elde edilen en ideal habitat uygunluk haritalarına göre, yaban tavşanı için uygun habitat tipine sahip alanlar; ibreli ormanlık alanlar, çalı step alanlar, ziraat alanları ve insan baskısından uzak çayırlık alanlardır. Yaban domuzu için uygun habitat tiplerinin; ormanlık alanlar, suya yakın alanlar, tür tarafından kazılabilen toprak tipine sahip alanlar ve insan baskısının olmadığı çayırlık alanlar olduğu belirlenmiştir. Porsuğun tercih ettiği habitatlar ise; çayırlık alanlar, kayalık alanlar, suya ve yerleşim yerlerine yakın alanlardır. Kaya sansarı için uygun habitat tipleri; orman içi açıklıklar, kayalık alanlar, ziraat alanları ve yerleşim yerine yakın alanlar olarak bulunmuştur. Artan yükselti ve eğimin; yaban tavşanı ve yaban domuzu habitat tercihinde pozitif yönde, porsuk ve kaya sansarı için negatif yönde etkili olduğu belirlenmiştir. Yaban tavşanı ve yaban domuzunun en fazla kuzeyli bakıları, porsuğun kuzeydoğu bakıyı, kaya sansarının ise güneybatı bakıyı tercih ettiği saptanmıştır. Anahtar Kelimeler: Potansiyel dağılım haritası, Bağlantı modelleri, Memeli büyük yaban hayvanları 2013, 249 sayfa
Thesis
Full-text available
Developing habitat suitability maps of wild animals is essential to generate ecosystem based management plans. Aim of this study was to develop annual and seasonal habitat suitability models and maps based on ecologic, topographic, and anthropogenic variables for the mammalian big wild animals which are brown hare (Lepus capensis L.), wild boar (Sus scrofa L.), badger (Meles meles L.) and beech marten (Martes foina L.) in the Gölcük district. Presence-absence method was used to determine habitat uses and relative habitat uses of the wild animals. Logistic regression analysis and regression tree methods were used as statistical analytical techniques. The validity of the models was confirmed by ten times cross-validation test. The models obtained for each species visualized through the Geographical Information System and in this way, habitat suitability maps achieved on the basis of locality. According to the best models obtained, the efficient habitat variables were young cedar stands, steppe, agricultural fields, meadowlands with little human pressure for the brown hare; forest existence, water sources, soils which can be easily, and meadowlands with little human pressure for the wild boar; meadowlands, proximity to residential areas and water sources, and rocky areas for the badger; and stand gaps, rocky areas, agricultural fields and proximity to residential areas for the marten. While increase in altitude and terrain slope negatively influences the habitat preference of the badger and marten, it positively influences the habitat preference of the wild boar and hare. The hare and wild boar mostly prefer northern aspects, the badger prefers northeastern aspects, and marten prefers southwestern aspects. Keywords: Potential distribution modals, Correlative modals, Mammalian big wild animals 2013, 249 pages
Article
Full-text available
The habitat choice of the small hindgut fermenter, the European rabbit (Oryctolagus cuniculus L.), was studied in relation to sward height, forage quality, population size fluctuations and spatial distribution of burrows in a temperate grassland. In a multi-phase differential clipping experiment with alternating short and tall vegetation strips, rabbits tended to graze near the closest burrows in situations of equal vegetation heights, while a clear preference for short swards was found during summer (July). In this period, general crude protein content was significantly lower than in spring (April) and autumn (September), apparently leading to a potential forage quality deficit. The summer behavioural pattern with short sward preference coincided with the relatively higher crude protein content of short swards as compared to tall swards in this period, and with higher intraspecific competition, due to significantly larger numbers of animals present in summer. In autumn, rabbit densities decreased, while crude protein content of both short and tall vegetation increased to a higher, though not significantly different level, comparable with spring crude protein content. In those conditions, significant preference for low vegetation height could no longer be detected. Data suggest that selection for nutritive quality appears when intraspecific competition is high and nutritive quality remains under a certain threshold value. When, in autumn, competition decreases and nutritive quality increases again, short sward preference disappears. We conclude that short sward preference is primarily caused by the better forage quality of re-growth in periods of forage quality limitation, while this preference disappears when forage quality limitation no longer occurs.
Article
Estimating population age structures by faecal pellets sizes is a commonly used field method in some mammal species. We examined the validity of this method in European rabbits based on 1113 pellets from 226 animals with known age, by measuring the intra-individual variation in pellet size and studying the explained variance of calibration curves describing the relation between pellet size and individual age. In addition, we applied a simulation model in order to estimate the accuracy of this method. Pellet size showed a high intra-individual variation and was only moderately correlated with the animals’ age. Modelling revealed that the population age structure assessed by this method deviated considerably from the given structure, indicating a systematic estimation error. We conclude that this method can lead to strongly biased results, restricting its validity. We provide estimation errors, which might be considered if estimates of age structure in wild rabbits populations based on faecal diameters are conducted.
Article
The ideal free distribution posits that at equilibrium habitats of all degrees of quality should have similar population growth rate (λ) values (≈1), but in fact sink habitats are often observed with λ < 1 when source habitats have λ > 1. This is the source-sink paradox. Animals appear to be choosing habitat that will lower their fitness. It is argued that the paradox can be resolved by considering individual decisions in a conditional choice model with non-identical individuals that differ in competitive ability and current expected reproductive output. Individuals that are more mature, healthier, and/or arrive earlier to the source will acquire territory at lower cost and will defend it more vigorously and effectively. For other individuals, costs (including running out of time for breeding) of acquiring territory in the source become so high that moving to the sink increases their fitness. The model is implemented in an individual-based modeling framework. The cost–benefit decision model unites previously disparate topics into a single framework, including protandry, territoriality, philopatry, and juvenile dispersal. Simulation results and a literature survey support predictions. Results indicate that individuals with lower competitive ability (e.g., juveniles) obtain a fitness advantage from moving to a sink. Random sorting of individuals (simple pre-emption) results in lower population λ than competitive sorting. The effective population λ in the source is increased and in the sink is decreased by competitive sorting such that individual and population λ are not simple functions of habitat quality. The theory and models developed link individual behaviours to population processes and resolve the source-sink paradox. It is suggested that metapopulation modeling theory needs to be revisited based on the results presented.
Chapter
Full-text available
The diverse origins of Mediterranean mammals have allowed various invasions during the course of the Middle and Upper Pleistocene: Eurasian and Ethiopian in North Africa, Irano-Turanian and Boreal in Europe. But these multiple invasions did not always lead to reciprocal extinctions as relaxation times seem to have been protracted in continental biotas. The saturated glacial faunas may have impeded high speciation rates in Mediterranean refugia. Most Mediterranean Pleistocene endemics evolved from depauperate insular faunas during several hundred thousand of years of isolation. Mediterranean mammals are thus representative of a wide range of geographic origins and habitats. Of particular interest is the fairly large number of brownsers characteristics of open landscapes, such as asses, gazelles, hamsters, gerbills and jerboas.
Article
Full-text available
As European rabbits Oryctolagus cuniculus (Linnaeus, 1758) in SW Spain face high predation pressure, some antipredator tactics are expected. We examined rabbit group size in relation to the safety of the cover (sparse or dense), and the proximity to shrub cover. Stem density influenced the distance rabbits ventured from shrub; rabbits ventured greater distances when stem density in cover was higher. Rabbit group size was related to the distance to cover; solitary animals remained closer to protective cover, whereas rabbits in groups (≤ 3 animals) foraged further from cover. These results are consistent with the hypothesis that the formation of rabbit groups is related to defense against predation, and that group size is influenced by risk of perception.
Article
Full-text available
This study assesses the effect of vegetation and variables related to weather and light conditions on the efficacy of rabbitOryctolagus cuniculus (Linnaeus, 1758) counts carried out in the south of Portugal. Counts were carried out in two years using driven line transects, and correlated with vegetation type and the variables using generalised linear models. The offset was a surveyed area estimated using Distance Sampling Theory as a means of correcting for detectability bias. More rabbits were observed in dense vegetation during day-time counts and in crops during night-time counts. In 1998, day-time counts were higher with higher average daily temperatures, whilst the night-time counts were higher with higher minimum daily temperatures. In 1999, day-time counts decreased with the amount of rainfall in the previous month, and the night-time counts decreased with the accumulated rainfall in the previous two months and with the higher wind speeds. In order to increase efficacy, counts should be carried out either at dawn or at dusk during the post-breeding season, and with greater intensity in dense scrub or open vegetation with high tree cover. During the breeding season and winter, counts should be carried out after dusk and with greater intensity in arable crops.
Article
Full-text available
The European rabbit (Oryctolagus cuniculus) is a key prey species in Mediterranean ecosystems and is ecologically plastic. However, ecological responses of rabbits to different habitats are poorly understood. We present data on abundance, distribution, activity, and survival in 3 neighboring habitats in southwestern Spain differing in refuge and forage availability. Scrubland presents dense cover but low forage abundance; grassland offers little protective vegetation but high food availability; the ecotone provides intermediate levels of both resources. Rabbits reached the highest abundance in ecotone, whereas low food and refuge availability seemed to limit their abundance in scrubland and grassland, respectively. In scrubland, rabbits were dispersed among the cover. In grassland, rabbits were linked to aggregated burrows. In ecotone, rabbits dug burrows in the bordering bushes that abutted grassy feeding pasture. Predation by raptors was low in scrubland, and mortality due to mammalian carnivores was higher in spite of more diurnal rabbit activity. Carnivore predation also caused higher mortality in grassland, where rabbits were more nocturnal. In ecotone, the effect of both mammalian carnivores and raptors on rabbits was similar. Mortality by disease seemed to be linked to level of rabbit aggregation.
Article
Full-text available
Disappearance speed of two signs of presence (isolated pellet groups and dunghills) of the wild rabbit Oryctolagus cuniculus was measured between May 1990 and July 1991 on two sites in Provence, southern France, to validate the use of the pellet group counts technique for this species in the French Mediterranean region. Four ecological factors were tested to explain the disappearance speed of isolated pellet groups and dung-hills : season, site, vegetation type and climatic parameters. Even if the results are more pertinent for dung-hills than for isolated pellet groups, the two signs of presence have the same general plan of disappearance. Our results show that season is the most important factor to be considered to sample the habitat-use of the wild rabbit. Using the pellet group counts technique, if any comparison is to be made, spring is the most favourable time of year because pellets disappear faster during this season. Whatever the season, if a comparison between several sites and biotopes is to be made, only fresh signs should be used. The influence of climatic parameters and the limits of pellet group counts technique are discussed.
Article
Full-text available
This study analyses differences in European rabbit Oryctolagus cuniculus (Linnaeus, 1758) abundance between fragmented and continuous populations and the relative importance of habitat structure (micro- and macrohabitat) and isolation in determining the abundance pattern in fragmented and continuous areas of central Spain. The species was mainly restricted to mediterranean vegetation habitat. In fragmented areas, rabbit abundance was linked to scrubland cover but was not correlated to pasture/cropland cover. The model explained very little of the observed variance. Distance to continuous populations did not improve the model. Stochastic phenomena or unmeasured factors (predation level, soil type) could be acting in this context. Rabbits were more abundant in continuous areas than in fragmented ones. In continuous areas, rabbit abundance was associated with mosaics of pastures, scrublands, and croplands. These habitat features are linked to shelter and feeding requirements of rabbits. The model explained an important part of the observed variance. This supports that management and conservation strategies should be based on the landscape pattern in each situation.
Article
Full-text available
Le rôle du lapin sauvage dans la dispersion des graines de Retama monosperma a été étudié dans les dunes d'une pointe de sable de la côte espagnole dans le comté de Hulva. Sur 8301 fèces de lapin récoltées au hasard, 2,4 % contenaient des graines de R. monosperma. Le pourcentage de fèces contenant des graines était significativement plus élevé en été et en automne. Le taux de germination des graines provenant de fèces était significativement plus élevé (24 %) que celui des graines extraites de fruits (13%). Les graines de R. monosperma avaient été dispersées sur toutes les crêtes de dunes inspectées dans la zone de colonisation et des fèces de lapin contenant des graines de R. monosperma ont été trouvées sur des dunes pas encore colonisées par des arbustes de R. monosperma. La dispersion des graines par le lapin est l'une des causes principales de la colonisation de R. monosperma sur la pointe El Rompido.
Article
Full-text available
From May 1983 to May 1985, sunset rabbit transect surveys (8.14 km long) were carried out on a weekly basis at Donana Biological Reserve (SW Spain). No changes in relative abundance were observed between years, however rabbit abundance showed abrupt seasonal changes. A bimodal pattern was observed, with maxima in June (mean: 8.34 rabbits/km) and December (3.59 rabbits/km), and the annual minimum in October (1.57 rabbits/km). Rabbit abundance was similar in shrubland (2.63 rabbits/km) and pastures close to marshland (2.28 rabbits/km), and significantly lower in both than in the transitional band between shrubland and pastures (9.08 rabbits/km). Rabbit abundance into the shrubland was significantly different between years, suggesting some intrapopulation movements influenced by environmental factors.
Article
Full-text available
European rabbit Oryctolagus cuniculus abundance was evaluated relative to habitat variables within two zones in Cadiz Province (south-east Spain), 2 years after the spread of rabbit viral haemorrhagic disease (RVHD). The study areas were low-lying regions of mixed pasture/agriculture, Mediterranean forest and matorral, west (Zone A) and east (Zone B) of the Sierra de Cadiz mountain chain. A total of 111 sites was selected to sample all existing habitat types. Relative rabbit density in each site was estimated using a pellet count method in one 50×2 m transect. Mean pellet densities were 21.05 pellet m-2 in Zone B and significantly lower, 5.85 pellets m-2 in Zone A. Physical variables, such as vegetation characteristics (density, height and patchiness of cover-layer vegetation, etc.), topographical characteristics and human influences, cover-layer vegetation species (woody stemmed shrub species or trees forming dense stands), and ground-layer vegetation species (herbaceous species forming a low-lying layer) were determined within transects. In addition to these variables, soil types, rock type and land form, as well as the presence of aquifers, irrigation, and the proximity of rivers, were determined for each site. Significantly higher pellet densities were found in mixed grassland/matorral and cork oak/matorral than in all other habitats. Pellet density was negatively correlated with density of ground-layer vegetation, while high pellet densities were associated with medium-height ground-layer vegetation (50–100 cm). The presence of Entisols was negatively associated with pellet density. The cover-layer species Pistacia lentiscus, Quercus coccifera, Quercus suber, Opuntia ficus-indica and the ground-layer grasses all showed positive associations with pellet density, while the ground-layer species Echium gaditana and Scorpiurus vermiculatus were negatively associated with pellet density. Multivariate analyses identified the mixed grassland/matorral and cork oak forest/matorral habitats as explaining most of the variation in pellet density. The height of cover-layer vegetation was negatively associated, while Opuntia and table-and/calcareous sandstone were positively associated, with mixed grassland/matorral. Distance from habitation and human impact were negatively associated and Quercus suber was positively associated with cork oak forest/matorral. Comparison with previous studies suggest that the low pellet counts in this study represent very low rabbit densities and the population as a whole appears depleted and fragmented.
Article
Full-text available
Several local populations of the otherwise trophic-generalist Eurasian badger (Meles meles) have been defined as specializing locally on temporally variable food resources such as earthworms (Lumbricus spp.), olive fruits (Olea europaea), or young rabbits (Oryctolagus cuniculus), owing to a lack of correlation between resource availability and use. However, theoretical models predict that temporal variation in resources reduces the probability of diet specialization. To understand the relationship between temporal resource variability and local feeding specialization, we studied temporal variation in diet composition and diversity (using fecal analysis), the availability of a temporally stable key resource, and the relation between consumption and availability of rabbits (key prey) and invertebrates (secondary prey) for a badger population previously described as specialized on young rabbits. We found strong variations in the use of different resources (including young rabbits) and in diet diversity among seasons and years. The main food resource was young rabbits during winter and spring, fruits in autumn, and reptiles in summer. Diet diversity was inversely related to consumption of young rabbits and directly related to consumption of secondary prey (invertebrates). Consumption of rabbits (both young and adults) was correlated with their abundance in the field, with a type 3 functional response in the consumption of young rabbits, which is typical of a generalist to whom alternative prey are available. There was no relationship between the abundance of invertebrates and their consumption. Our results show that badgers in the study area were not locally specialized, therefore care should be taken when referring to a population as specialized without an adequate test of the predictions.
Article
Full-text available
Can the interaction of episodic and chronic disturbances explain the maintenance of savanna-like patterns? We explored the morphological and spatial patterns of the leguminous shrub Retama sphaerocarpa in a Mediterranean environment in relation to disturbance. Various morphological variables of R. sphaerocarpa shrubland were found to be determined by a combination of two types of disturbance: (1) mechanical cutting: an episodic, heavy, short-term disturbance of anthropogenic origin for management purposes, and (2) herbivore activity primarily by rabbits: generally a chronic, more lenient, long-term disturbance. The intensities of these two types of disturbance were not correlated. Mechanical cutting effects on R. sphaerocarpa shrubland morphology predominated quantitatively over herbivore effects. Herbivores generally produced open shrubland with fewer, more scattered, thicker branched, larger R. sphaerocarpa shrubs. In contrast, intense sprouting after cutting produced a higher density of smaller R. sphaerocarpa shrubs with denser aerial biomass. However, heavy herbivory in abnormally dry periods produced some effects similar to those of mechanical cutting. The size of R. sphaerocarpa shrubs was positively related to seed production. Thus, the means of propagation depended upon the type of disturbance: episodic disturbances resulted in intense sprouting, whereas chronic herbivore activity resulted in the formation of thick branches that produced a large number of seeds. The combination of these two disturbances determine, in part, space occupancy patterns of dominant woody species in this Mediterranean landscape and similar savanna-type ecosystems. Investigations of environmental constraints on vegetation distribution and abundance should take into account the historical role of herbivores in shaping present systems.
Article
Full-text available
The Wild rabbit (Oryctolaguscuniculus) is an endemic species of the Iberian Peninsula and is essential for the conservation of endangered predators. Rabbits are also of high importance as a hunting species. From 1988, rabbits suffered the severe effects of rabbit hemorrhagic disease, which caused large declines in most populations. Despite this fact, the National Red Data Lists continued to classify rabbits as a “Least Concern” species. We used available hunting bag data from 1973 to 2002 to model national trends of rabbit abundance and to evaluate the conservation status according to the criteria of the National Red Data List and the World Conservation Union (IUCN). Generalized Additive Models were used as the statistical framework. The rabbit population of Spain suffered a large decline of about 71% between 1973 and 1993. This decline was 49% in the period 1980–1990. Based on both Spanish and World Conservation Union criteria, rabbits should be listed as ‘Vulnerable’, which demands a Conservation Plan Program. We suggest that the lack of concordance between the best available evidence and the conservation status of the species is a consequence of sociological constraints in conservation decisions. Rabbit conservation could face strong opposition from important socio-economic lobby groups (hunters and farmers). As such, governments and researchers may prefer to exclude rabbits from any status category requiring conservation action, despite the evidence of decline. We call for the urgent development of a nation-wide conservation program for rabbits which includes both socioeconomic constraints and the available biological data on population trends. KeywordsDecline-GAM-Haemorrhagic disease-Hunters-Population trends-Rabbit-Spain-Threatened species
Chapter
Full-text available
Beyond their role as primary consumers, herbivore activities can play a key part in spatial processes at the ecosystem level (e.g., McNaughton 1983; McInnes et al. 1992; De Miguel et al. 1997). Environmental factors such as geomorphology, soil and vegetation characteristics, slope, aspect etc., affect the spatial distribution of the resources they need, mainly refuge, food, and water. Therefore, a particular set of habitat characteristics influences the use of different areas for specific activities by a given herbivore species. In turn, the use of habitats by herbivores may affect such characteristics at different scales. This is the case of many sedentary herbivores which, after establishing themselves in a particular area of an ecosystem, begin their modification. Pond construction by beavers not only changes river-flow patterns and surrounding vegetation, but also nutrient cycling (Naiman et al. 1994; Pollock et al. 1995). Excavating mammals, such as prairie dogs and pocket gophers, can also have profound impacts upon soil processes and the vegetation surrounding their burrow systems (see Whitford and Kay 1999; Huntly and Reichman 1994 for thorough reviews). Species that can have significant effects on the spatial structure of the landscape and the distribution of resources, both for themselves and other organisms, are considered ecosystem engineers (Jones et al. 1994). These species can be important patch creators through their activities or structures, and these patches can be exploited by different animal and plant species, thus increasing biodiversity and potentially controlling many processes and affecting ecosystems at different scales.
Article
Full-text available
Rabbits (Oryctolagus cuniculus) have been recently introduced to central Chile; adult rabbits have been previously reported to exhibit a release in their use of microhabitats due to lack of effective predation upon them. This paper shows that kittens and juvenile rabbits do not exhibit the same microhabitat use pattern as adults, in spite of the very low predation pressure upon them. These results suggest that small rabbits are ecologically comparable to native rodents.
Article
Full-text available
According to classical exploitation theory, an increase of primary productivity should result in increased herbivore grazing pressure, thus maintaining a low plant standing crop. However, field data obtained from a salt marsh revealed a maximal grazing pressure by hares, rabbits, and geese at intermediate levels of plant standing crop. Grazing pressure was relatively low in the more productive parts. We argue that this pattern is due to a low foraging efficiency of these herbivores in dense vegetation. In order to investigate this hypothesis, we examine a plant-herbivore model where grazing becomes less efficient in dense vegetation, and analyze the behavior of this model along a gradient of primary productivity. In systems of intermediate productivity, the model predicts that a plant-herbivore system may have two stable states. In one state, the herbivore maintains a low standing crop. The other state is dominated by a dense vegetation unsuitable for herbivore grazing. In systems of high productivity, the herbivore is unable to keep plant growth in check and a dense vegetation develops. Thus, in line with our field data but in contrast to classical exploitation theory, our model does not predict "top-down" control in productive environments.
Article
Full-text available
Natal dispersal and philopatry have rarely been studied in tropical forest raptors. Especially with respect to endangered species with fragmented distributions more knowledge of dispersal and age-related habitat preferences is needed for proper management. We conducted an island-wide study on age-related habitat preferences of the endangered Javan Hawk-eagle (Spizaetus bartelsi), Indonesia's national bird. The Javan Hawk-eagle is a true forest eagle, but is occasionally observed in non-forested areas. On the basis of 95 visual encounters in 50 localities in the period 19802002, we established that there were no age-related differences in geographical, altitudinal or climatic distribution. In habitat preferences, however, juveniles and immatures are proportionally more often recorded in open and disturbed habitats than adults, which seem to have a greater preference for evergreen forest. These results indicate that the prime habitat for adult Javan Hawk-eagles is evergreen forest and to a lesser degree secondary forest, with juveniles dispersing out of their natal territory into different habitat types, including seemingly unsuitable types. In their habitat choice, immatures tend to be more similar to adults than to juveniles, which is an indication that their dispersal takes place into habitats that are more suitable for establishing a breeding territory.
Article
Provides information on 197 mammal species of different regions of the Mediterranean Basin, and comments on: species richness; species invasion stages and extinction processes; changes in the Pleistocene mammal fauna of North Africa, the Levant and Mediterranean Europe; island changes; and post-Pleistocene invasions. Saturated glacial faunas may have impeded high speciation rates in Mediterranean refugia. Most Mediterranean Pleistocene endemics evolved from depauperate insular faunas during several hundred thousands of years of isolation, while the last glacial covered at most 70 000 yr, a short time for differentiation of most mammalian populations. The best supported example of speciation in European refugia comes from the Arvicolidae. Islands and mountains have been as effective in promoting speciation among Mediterranean biotas as Pleistocene refugia. Adaptive radiation in a patchy environment, which probably reduced gene flow among populations, accounts for most of the Pleistocene speciations in North Africa. -P.J.Jarvis
Article
This chapter gives results from some illustrative exploration of the performance of information-theoretic criteria for model selection and methods to quantify precision when there is model selection uncertainty. The methods given in Chapter 4 are illustrated and additional insights are provided based on simulation and real data. Section 5.2 utilizes a chain binomial survival model for some Monte Carlo evaluation of unconditional sampling variance estimation, confidence intervals, and model averaging. For this simulation the generating process is known and can be of relatively high dimension. The generating model and the models used for data analysis in this chain binomial simulation are easy to understand and have no nuisance parameters. We give some comparisons of AIC versus BIC selection and use achieved confidence interval coverage as an integrating metric to judge the success of various approaches to inference.
Chapter
Perhaps only the English with their unwitting natural irony could have retained the name New Forest for an area that is neither new (it is one of the oldest semi-natural areas of woodland in Great Britain, as well as one of the largest) nor what most would regard as a forest. ‘New’ only when it was first created the latest in a series of ‘Royal Forests’ in the eleventh century, it is also a ‘forest’ only in the medieval sense of an area set aside as a royal hunting preserve (and thus coming under Forest rather than Common law). Set in the Hampshire Basin of southern England, between the Solent and the Avon (Figure 2.1) this ‘New Forest’ comprises a diverse mix of vegetational communities: only some 10 000 ha (of a total administrative area at the current time of approximately 37 500 ha) are actually forested in the sense of covered with trees; the remaining area is a complex mosaic of open heathland, grasslands and bog.
Article
(1) The distribution pattern of the European wild rabbit in the Reserva Biologica de Donana is described in relation to an objective landscape analysis of the study area. (2) The landscape consists of three principal sand dune land systems, the youngest of which is still forming, lying between the Atlantic Ocean and the alluvial deltaic plain of the Rio Guadalquivir, Las Marismas. The climate is one of hot dry summers and mild wet winters. Las Marismas and smaller border areas of the sandy land systems form seasonal marshes each winter. (3) Rabbits are distributed discontinuously and are concentrated near moist grassland areas near borders of land systems. (4) Detailed distribution patterns in apparently favourable and unfavourable areas showed that rabbits thrive best where sand ridges suitable for warren building interdigitate or abut moist feeding grounds. (5) It is suggested that the dynamics of distribution and numbers superimposed on objective landscape analysis allows sensible wildlife management decisions to be taken in the absence of more detailed parametric study.
Article
Yellow-bellied marmots (Marmota flaviventris) in the White Mountains of eastern California spent 10.2% of their foraging time on vigilance (looking up), a behavior which is necessary for predator avoidance but which reduces the rate of food intake. More time was spent looking up when alarm calls were emitted by conspecifics than in the absence of calls. Vigilance time was reduced when marmots fed in groups and in areas with many safety burrows and low vegetation. These observations suggest that the cost of antipredator behavior, expressed as a reduction in feeding rates, may be minimized by adjusting the time spent on vigilance in response to the risk of predation. Juveniles and yearlings spent more time looking up while feeding than did adults. Juveniles were also more responsive to the factors that influenced vigilance than were older animals. This may be due to the greater nutritional demands of young animals together with their higher susceptibility to predation.
Article
European rabbits (Oryctolagus cuniculus) are of special concern, for different reasons. They are prey of many predators in Mediterranean ecosystems, an important game species, and even a pest that causes economic losses. Hence, estimate of population abundance is a major interest for conservation management and control programs. I estimated abundance of European rabbits in 6 different habitats by line transect sampling, pellet count, and warren count. Rabbits were most abundant in Mediterranean scrubland, closely followed by ash stands. Pastureland, lentiscus in plantations, and pine plantations had 3, 7, and 27 times fewer rabbits than the Mediterranean scrubland, respectively. Abundance determined by pellet counts corroborated results obtained by line transect sampling, except in the Mediterranean scrubland habitat, where number of pellets was less than expected. There was a significant correlation between number of pellets and rabbit density when data from the Mediterranean scrubland were replaced by data from pellet counts performed at the edge of the Mediterranean scrubland. Number (mean±SE) of warrens/100 m of transect was greatest for Mediterranean scrubland (3.5±0.5) and least for pastureland (0.6±0.2). Number of entrances/warren also differed among habitats; warrens in the pastureland had more entrances (11±1.2) than warrens in other habitats (between 5.5±0.6 and 9.0±1.2). Entrances were used more during spring (54.8%±4.3-74.6%±2.4) than during summer; the only habitat where entrances were used regularly in summer was the pastureland (54.6%±4.2 of entrances). Counting pellets and warrens can provide reliable estimates of rabbit abundance.
Article
Antipredator vigilance behaviour is affected by a number of variables, but studies reporting experimental manipulation of visual obstructions are generally lacking in the literature. We examined the individual antipredator behaviour of free-ranging thirteen-lined ground squirrels in 7 city parks in Lincoln, Nebraska, USA as they fed on peanut butter within small plexiglass boxes. Boxes differed in the position and amount of visual occlusion for a squirrel feeding in it: opaque, clear, opaque-sides, and opaque-top (also opaque on the end). We experimentally controlled environmental and contextual variables that have been identified as affecting vigilance behaviour. We filmed 38 ground squirrels as they fed in the boxes, and the results indicate that ground squirrels treat lateral occlusion as functionally identical to complete occlusion. Additionally, there were no significant differences in the squirrels' behaviours in the clear versus the opaque-top box. In 35 approach tests, a person walked toward individual ground squirrels as they foraged in one of the 4 box types. The distance at which the squirrels reacted did not differ among the 4 box types. The results of these two experiments suggest that thirteen-lined ground squirrels compensate for visual occlusion, primarily through increased withdrawals coupled with low-level vigilance postures and that the position of visual occlusion can be of greater importance than the absolute amount of occlusion.
Article
The study site was a dune system with short grass, and the tests were carried out with a predatory bird dummy and a ferret Mustela putorius. Confrontation with the dummy indicated a higher level of reactions in inexperienced young rabbits; this was the only age class which reappeared from their holes within 30 minutes of a dummy predator test. Experienced rabbits of all ages always responded to the bird dummy, escaping more frequently than inexperienced rabbits into their burrows, and peeping out again within 30 minutes. Comparison with responses to the ferret showed that only the experienced young rabbits reacted more frequently to the bird dummy than to the ground predator. Experienced older rabbits escaped more frequently after confrontation with the dummy than from confrontation with the ferret inside the burrow, whereas experienced younger rabbits were 8 times more likely to be caught by the ferret. -J.W.Cooper
Article
In the ovaries of wild yearling rabbits the histologic changes occurring between September and March were determined and related to age and season. It was found that a considerable part of the ovarian development is characterized by the growth of follicles which soon become atretic and form interstitial gland tissue. The ovarian development up to a “sub-ovulatory” stage may be completed in the autumn in rabbits born early in the season, and later in those born late, so that by mid-winter they are all in this stage. No ovulation was found in rabbits in the early stages of development, and it is suggested that the presence of interstitial tissue is essential for full reproductive capacity.
Article
An electrofishing survey of daytime shelter microhabitat use of bullhead Cottus gobio in a southern English chalk stream revealed positive selection for moderate water velocity, vegetation cover and coarse substrata. Water depth, other forms of cover, shade and substratum embeddedness had no significant influence on the distribution of fish. Microhabitat use was size‐dependent, with patches occupied by adult fish containing coarser substrata and less blanket weed (Cladophora algae) than those occupied by smaller juvenile conspecifics. Differences in substratum use between size‐classes were less pronounced in parts of the stream shaded by the tree canopy. In laboratory tanks stocked at low fish density, both juveniles and adults favoured use of cobbles over pebbles. The response of fish to increased conspecific density was size‐dependent; juveniles reduced use of the coarse substratum whereas adults maintained their predominance in this habitat. An apparently greater shift by juveniles when in the presence of adults was significant at α = 0·10 only, as was an apparent reduction in interactions between size‐classes under low light intensity. The displacement of small juvenile fish from the preferred cobble substratum is consistent with the hypothesis that intraspecific competition contributes to the size‐related microhabitat shift observed in the field. Although there was a tendency for the strength of competition to be reduced at low light levels, the mechanism by which tree canopy cover affects microhabitat use remains uncertain.
Article
This study examines the behavioral mechanisms underlying changes in the time allocation patterns of black-tailed prairie dog (Sciuridae: Cynomys ludovicianus) pups. Previous analyses of time budgets had revealed substantial differences between pups (young of the year) and adults, and that pup time budgets changed significantly over time. This paper shows that these differences were due to two mechanisms: pups generally differed from adults in the frequency of performance of different behaviors; however, changes in pup behavior over time were due to changes in both bout frequencies and durations. Other influences on bout durations were also examined. Time of day dramatically affected the duration of most behaviors, with vigilance bouts longest in the morning and feeding bouts longest in the evening. The presence of a pup's mother above ground and the height of the vegetation a pup was in had much less influence on bout durations. Multiple regression analyses were used to identify other potential influences (e.g., weather and social conditions) on bout lengths. Of these, the distance of a pup from the nearest burrow produced the strongest relationships.
Article
Natal dispersal of European wild rabbits,Oryctolagus cuniculus, was studied in a 2-ha outdoor enclosure between 1988 and 1990. The rabbit population had been established in 1984 and by 1988 it was structured into nine territories. The enclosure conditions allowed detailed study of dispersal of individual juveniles from their natal territories. Eighty-eight per cent (first year) and 65% (second year) of juveniles that survived until the beginning of their first breeding season dispersed. Dispersers either moved into other pre-existing territories (68%), established previously unoccupied territories (21%), or became non-territorial satellites (11%). Dispersal was male-biased with 93% of juvenile males and 64% of juvenile females dispersing. Female dispersers most often moved to neighbouring territories whereas male dispersers moved further away. At the beginning of their first reproductive season females that remained on their natal territories produced significantly more offspring than those that dispersed. Natal dispersal occurred during the first 5 months of life. The first breeding occurred in the following spring. During the period when dispersal occurred, aggressive interactions were uncommon among juveniles or between adults and juveniles. During 87 30-min observation periods, only 15 aggressive interactions were counted, only one of which was initiated by a member of the natal territory. All possible 26 pairs of opposite-sex littermates occupied different territories at the beginning of their first breeding season. In conclusion, natal dispersal in wild rabbits was not caused by aggression. Animals left the natal site on their own volition and settled down where no close relatives were present.
Article
Aim To document geographical interspecific patterns of body size of European and North American squamate reptile assemblages and explore the relationship between body size patterns and environmental gradients. Location North America and western Europe. Methods We processed distribution maps for native species of squamate reptiles to document interspecific spatial variation of body size at a grain size of 110 × 110 km. We also examined seven environmental variables linked to four hypotheses possibly influencing body size gradients. We used simple and multiple regression, evaluated using information theory, to identify the set of models best supported by the data. Results Europe is characterized by clear latitudinal trends in body size, whereas geographical variation in body size in North America is complex. There is a consistent association of mean body size with measures of ambient energy in both regions, although lizards increase in size northwards whereas snakes show the opposite pattern. Our best models accounted for almost 60% of the variation in body size of lizards and snakes within Europe, but the proportions of variance explained in North America were less than 20%. Main conclusions Although body size influences the energy balance of thermoregulating ectotherms, inconsistent biogeographical patterns and contrasting associations with energy in lizards and snakes suggest that no single mechanism can explain variation of reptile body size in the northern temperate zone.
Article
Life-table data of 56 natural populations of mammals were analysed, modelling mortality rate as a three-phase step function of age (the step model) instead of using the Gompertz model. In the step model, mortality rale is constant in each phase. The phases correspond to juveniles and young and old adults. The age of transition between young and old adults is referred to as the age of senescence. This approach has the advantages that, for the first time, the age of senescence is identified objectively using a robust statistical procedure, and that young adult mortality rates are estimated without bias since no assumption is made about how adult mortality rate changes with age. A further statistical problem solved here that has previously caused difficulty is that of correctly accounting for the different levels of precision in data from different age classes. Significant changes (P < 0.05) in adult mortality rate with age were found in 27 out of 56 populations. In 23 of these 27 cases, adult mortality rate increased with age. Juvenile mortality rate differed significantly from young adult mortality rate in 21 cases; in 18 of these the rate for juveniles was higher. These results are discussed in relation to earlier analyses, in particular that of Promislow (1991).
Article
The seasonal and spatial pattern of diet composition of a population of wild rabbits Oryctolagus cuniculus L. occupying a southern Portuguese montado was estimated using the n-alkane technique. The diet was analysed in terms of components that are relevant to habitat management. The dietary categories considered were gum cistus leaves and flowers, cork oak and holm oak seedlings and acorns, cereals, olive tree regrowth and grass-forb species. The objectives were to assess the changes in diet across seasons in relation to the reproductive cycle of the rabbits, and to relate these changes to herbaceous biomass availability and to habitat structure, in terms of density of scrub cover and accessibility to arable crops. The results demonstrated that the diet was dominated by grass-forbs, and cereals when they were available. Browse was an important component of the diet and became more important in a year of low herbaceous biomass availability and in areas dominated by dense scrub. A similar phenomenon was observed in relation to consumption of acorns in winter. Seasonal and spatial variation in diet composition suggested a strategy aimed at maintaining a high quality diet. This was supported by the observed high dry matter digestibility of the diet during most of the year. The relevance of growing arable crops and providing fodder, as a means of increasing the carrying capacity of montados for rabbits and protecting the natural regeneration of trees, is discussed.
Article
Natal dispersal and philopatry have rarely been studied in tropical forest raptors. Especially with respect to endangered species with fragmented distributions more knowledge of dispersal and age-related habitat preferences is needed for proper management. We conducted an island-wide study on age-related habitat preferences of the endangered Javan Hawk-eagle (Spizaetus bartelsi), Indonesia's national bird. The Javan Hawk-eagle is a true forest eagle, but is occasionally observed in non-forested areas. On the basis of 95 visual encounters in 50 localities in the period 1980–2002, we established that there were no age-related differences in geographical, altitudinal or climatic distribution. In habitat preferences, however, juveniles and immatures are proportionally more often recorded in open and disturbed habitats than adults, which seem to have a greater preference for evergreen forest. These results indicate that the prime habitat for adult Javan Hawk-eagles is evergreen forest and to a lesser degree secondary forest, with juveniles dispersing out of their natal territory into different habitat types, including seemingly unsuitable types. In their habitat choice, immatures tend to be more similar to adults than to juveniles, which is an indication that their dispersal takes place into habitats that are more suitable for establishing a breeding territory. Philopatrie und die Ausbreitung von Jungtieren sind bei tropischen Raubvögeln bislang kaum untersucht, obwohl gerade für bedrohte Arten mit fragmentierten Verbreitungsgebieten ein besserer Kenntnisstand über die Ausbreitungsmuster und altersbedingte Unterschiede in den Habitatvorlieben für ein effektives Management notwendig wäre. In der Zeit zwischen 1980 und 2002 führten wir eine inselweite Studie über altersbedingte Habitatpräferenzen des Javahaubenadlers (Spizaetus bartelsi) durch. Diese Art, Indonesiens Nationalvogel, ist auf Waldgebiete spezialisiert, kann aber gelegentlich auch in unbewaldeten Gebieten beobachtet werden. Die Analyse von 95 Sichtbeobachtungen an 50 Fundorten zeigte keine altersbedingten Unterschiede in der geographischen, höhenbedingten oder klimatischen Verbreitung, wies aber dagegen auf eine unterschiedliche Habitatwahl juveniler und subadulter Adler hin. Diese wurden signifikant häufiger in offenen und degradierten Gebieten beobachtet, während die adulten Tiere eine stärkere Präferenz für geschlossene Regenwaldgebiete aufwiesen. Die Fortpflanzung des Javaadlers findet meist im Regenwald statt, und die frisch ausgeflogen Tiere zeigen ähnliche Habitatvorlieben wie die Adulti. Dies bestätigt, dass der Regenwald den primären Lebensraum des Javaadlers darstellt und die Jungtiere sich in andere, darunter auch anscheinend weniger geeignete, Habitate ausbreiten. Die subadulten Tiere zeigen dagegen Habitatpräferenzen, die stärker an die der Altvögel erinnern als an die der Juvenilen. Dies weist möglicherweise darauf hin, dass sie in dieser Lebensphase bereits Bereiche suchen, die als Brutterritorium geeignet sind.
Article
Ontogenetic shifts in habitat use are widespread, especially in ectothermic taxa in which juveniles may be an order of magnitude smaller than large adult conspecifics. The factors that generate such habitat shifts are generally obscure, but we studied an unusual system that allowed us to compare consequences of habitat selection between adults and juveniles. Pit-vipers (Gloydius shedaoensis) on a small island in north-eastern China feed almost entirely on seasonally migrating birds. During the spring bird-migration period, individual snakes consistently re-used either arboreal or terrestrial ambush sites. Snakes in trees were smaller (and more philopatric) than snakes on the ground. This ontogenetic shift in habitat use may reflect the difficulty of capturing birds on the ground, especially by small snakes. In laboratory trials, large (adult) pit-vipers struck faster, further and more accurately than did small (juvenile) snakes. In experiments with free-ranging snakes, the proportion of strikes hitting the bird was lower for juveniles than for adults, and lower for terrestrial snakes than for arboreal snakes. Additionally, adult snakes generally seized the bird by the head whereas juveniles frequently struck the body or wings (and thus, obtained a less secure grip). Arboreal ambush sites may facilitate prey capture not only because they give access to smaller birds but also because they render the bird's location more predictable and, hence, enable the snake to position itself optimally prior to the prey's arrival. Because juvenile pit-vipers are less capable strikers, and are small relative to available prey items, they may benefit from the greater ease of prey capture from branches. Thus, the ontogenetic shift in habitat selection within this species may be because of ontogenetic shifts in the vipers’ ability to capture and ingest large, mobile prey.
Article
Warrens of the wild European rabbit Oryctolagus cuniculus are of concern in the Iberian Peninsula as a way to recover rabbit populations. However, there are no studies on the selection of sites where rabbits build their warrens. Between 1995 and 1997, in addition to warren size (number of entrances), the vegetation characteristics and the occurrence of tree roots in the ground surface occupied by warren entrances in Mediterranean scrubland and pastureland habitats were recorded in a sandy area of the Doñana National Park. Pastureland warrens were about twice as large as warrens in Mediterranean scrubland, and 1.8–1.4 times larger in the first study year than in the other 2 years. Warrens in pastureland were built more between tree roots (13.3–17.8%) than those built in Mediterranean scrubland (0.7–1.8%). In Mediterranean scrubland, most of the ground surface occupied by warren entrances was under tall shrubs (79.7–87.9%), with some under short shrubs (4.5–7.4%). In pastureland, these figures were 2.0–3.8% for tall shrubs, and 17.2–19.8% for short shrubs. Warrens were built between tree roots significantly less than expected in the Mediterranean scrubland, and slightly more than expected in the pastureland. Whereas warren surface was occupied by short shrubs significantly less than expected in the Mediterranean scrubland, the opposite pattern occurred in the pastureland; however, in both habitats tall shrubs were significantly preferred. These results suggest that rabbits may seek protection against collapsing warrens by selecting sites with some supporting structures such as the roots of trees or shrubs. Scrubland vegetation (preferably tall shrubs) should be favoured for medium- and long-term habitat management of areas aimed at supporting large rabbit populations. Furthermore, in sandy areas, some kind of stable ground support and external protection should be provided when creating artificial warrens for rabbits.
Article
1. The relationship between available biomass and short-term rate of intake (functional response) of herbivores is expected to provide a link between their food supply, and their distribution. 2. The functional response of captive wild rabbits (Oryctolagus cuniculus L.) on artificially produced broad-leaved (Lolium perenne L.) and narrow-leaved (Festuca ovina L.) grass swards was quantified. 3. The general prediction that habitat selection varied with biomass, and reflected the potential rate of intake defined by the functional response, was also tested. The main alternative predictions, that both intake rate and habitat selection increased asymptotically with biomass, or were biased towards intermediate habitat standing crop biomasses, were distinguished. 4. There was no relationship between biomass and short-term rate of intake on the narrow-leaved Festuca swards, but on the broad-leaved Lolium sward the short-term rate of intake increased asymptotically with biomass. 5. In a field experiment on Lolium swards, a population of free-living wild rabbits selected the shortest swards with the lowest biomasses, and which provided the lowest potential rates of intake. 6. Results demonstrate that free-living wild rabbits do not select habitats that provide the maximum potential rate of intake, nor did they select foraging habitat with intermediate standing crops. It is suggested that their selection of foraging areas in these grasslands which typify rabbit foraging habitat, is dominated by antipredator considerations rather than purely by rate of intake.
Article
Populations of European wild rabbit (Oryctolagus cuniculus) have been decreasing since the 1950s. Changes in agricultural practices have been suggested as reasons for their decline in Mediterranean landscapes. We evaluated the environmental variables affecting rabbit distribution in a semiarid agricultural landscape of Northeastern Spain. Sampling was performed in 147 sites randomly distributed across Zaragoza province. At each site, data were recorded in five 100 m segments along a 1 km transect, following ecotones between crops and natural-vegetation areas. A rabbit abundance index was estimated from latrine count, pellet density and number of plots with pellets. In addition to environmental variables that have been shown to be related to rabbit abundance in other habitats, as climate, soil hardness and topography of the site, we measured landscape components related to agricultural use, such as structure of natural vegetation in remaining areas non-devoted to agricultural use and distances to different types of crops and to ecotone between crop and natural vegetation. Our results showed that rabbit abundance was positively correlated to yearly mean temperature, February and May mean rainfall, and negatively correlated to September and November mean rainfall, hardness of soil, and site topography. In relation to agricultural use, rabbit abundance was positively correlated to the scrub structure of natural-vegetation areas and negatively correlated to distance to edge between cultivated unirrigated cereal crops (wheat or barley) and yearly resting cereal crops. Rabbit abundance increased only when the edge between alternate cereal crops was less than 50 m from the ecotone between crops and natural vegetation.
Article
A method for estimating body mass of European rabbitsOryctolagus cuniculus (Linnaeus, 1758) based on tooth dimensions is proposed. Regression models identified significant relationships between the body mass of 87 rabbits and individual tooth length, breadth, product of tooth length and breadth, and whether or not the individual was infected with myxomatosis. Dimensions of 10 of 14 different teeth explained over 80% of variation in body mass, and those teeth were selected as adequate predictors of rabbit body mass. Models were tested using teeth from 16 additional rabbits of known body mass. Body mass, predicted on the basis of 9 of the 10 selected teeth, was statistically indistinguishable from the observed values for all 16 individuals. When myxomatosis infection status of the rabbit was included in the model, all 10 selected teeth yielded predictions statistically indistinguishable from those observed. Prediction errors can be computed permitting statistical comparison of the average predicted value of body mass from different samples of rabbits. The model is useful in estimating rabbit body masses from teeth recovered from feces of predators and it will facilitate testing of hypotheses on size-selective predation. The method was applied to rabbit teeth found in fecal samples from the Iberian lynxLynx pardinus collected over a one-year period. Lynx preyed preferentially upon younger rabbits during the peak breeding period of this lagomorph. Key words Oryctolagus cuniculus - Lynx pardinus -body mass prediction-prey remains-size selection
Article
The social structure and demography of a free-living rabbit population, living on a 10ha bowl of chalk downland in Oxfordshire, England, were studied for 6yr. The population was divided into 11-14 breeding groups, each containing 1-8 males and 1-12 females. Some 89% of males and 96% of females lived in groups containing at least one other rabbit of the same sex. Nest sites were both localized and limited in their availability, which imposed a group-living habit on many females. These female groups attracted males up to an average group sex ratio of 1.5 females per male. Females living in groups containing >1 female had lower 'lifetime reproductive success' than those that lived with males only. Hence, the costs of group living apparently outweighed the potential benefits. Also male survivorship did not increase with group size. -from Author
Article
A keystone species is one that is crucial in maintaining the organization and diversity of their ecological communities. We tested the idea that rabbits act as a keystone species in southern Europe by exploring relationships between rabbit abundance and the abundance and diversity of raptor species. At 20 sites in southern Spain we assessed rabbit abundance through counts of animals along transects and assessed the number of raptor individuals and species through watches from vantage points. In a further 120 locations we also derived an index of rabbit abundance, from pellets and compared this to the presence or absence of the critically endangered Spanish imperial eagle. Rabbit abundance was positively associated with the number of observations of raptors, the number of raptor species and the number of species of conservation concern. Sites with the most rabbits had higher conservation value. Moreover, the presence of Spanish imperial eagle was strongly associated with sites where rabbits were at high density. We conclude that rabbits do act as a keystone species and we suggest that conservation efforts should focus on improving the status of this small-game species in southern Europe.
Article
Several endangered carnivores and raptors in Mediterranean Spain are very dependent on rabbits Oryctolagus cuniculus, which have shown a progressive decline in abundance for several decades. Land use neglect, and the consequent abandonment of traditional land use methods such as burning, is considered one of the factors responsible for this decrease. To examine this hypothesis we have compared rabbit use of experimentally burned and unburned scrubland areas. Rabbit activity was found to be significantly higher in burned areas, with the greatest use in less productive habitats in close proximity to scrub cover. The promotion of traditional land practices for nature conservation in the natural ecosystems of the Mediterranean Basin is discussed.
Article
Autocorrelation is a very general statistical property of ecological variables observed across geographic space; its most common forms are patches and gradients. Spatial autocorrelation, which comes either from the physical forcing of environmental variables or from community processes, presents a problem for statistical testing because autocorrelated data violate the assumption of independence of most standard statistical procedures. The paper discusses first how autocorrelation in ecological variables can be described and measured, with emphasis on mapping techniques. Then, proper statistical testing in the presence of autocorrelation is briefly discussed. Finally, ways are presented of explicitly introducing spatial structures into ecological models. Two approaches are proposed; in the raw-data approach, the spatial structure takes the form of a polynomial of the x and y geographic coordinates of the sampling stations; in the matrix approach, the spatial structure is introduced in the form of a geog
Article
Wildlife-Habitat Relationships goes beyond introductory wildlife biology texts to provide wildlife professionals and students with an understanding of the importance of habitat relationships in studying and managing wildlife. The book offers a unique synthesis and critical evaluation of data, methods, and studies, along with specific guidance on how to conduct rigorous studies. Now in its third edition, Wildlife-Habitat Relationships combines basic field zoology and natural history, evolutionary biology, ecological theory, and quantitative tools in explaining ecological processes and their influence on wildlife and habitats. Also included is a glossary of terms that every wildlife professional should know. Michael L. Morrison is professor and Caesar Kleberg Chair in Wildlife Ecology and Conservation in the Department of Wildlife and Fisheries Sciences at Texas A&M University in College Station. Bruce G. Marcot is wildlife ecologist with the USDA Forest Service in Portland, Oregon. R. William Mannan is professor of wildlife ecology at the University of Arizona in Tucson.
Article
A population of thirteen-lined ground squirrels in Madison, Wisconsin, was studied during the spring and summer of 1961 and 1962. Conception dates varied within and between years. Males moved greater distances than females. Spring seemed to be the period when longest movements took place. Adults had a 29% annual survival rate, juveniles, only 16%. Females had a higher survival rate than males. High mortality among juveniles mainly occurred prior to hibernation. Three distinct types of burrows were noted.