Article

Mate guarding, reproductive success and female choice in African elephants

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Abstract

Male guarding of females, male mating success and female choice were studied for 8 years among a population of African elephants, Loxodonta africana. Males were not able to compete successfully for access to oestrous female until approximately 25 years of age. Males between 25 and 35 years of age obtained matings during early and late oestrus, but rarely in mid-oestrus. Large musth males over 35 years old guarded females in mid-oestrus. Larger, older males ranked above younger, smaller males and the number of females guarded by males increased rapidly late in life. Body size and longevity are considered important factors in determining the lifetime reproductive success of male elephants. Oestrous females exercised choice by soliciting guarding behaviour from musth, but not non-musth males. Females in mid-oestrus gave loud, very low frequency calls that may attract distant males and incite male-male competition. The behaviour of oestrous females resulted in their mating with males who were old, vigorous and healthy.

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... Although poaching for ivory concentrates on single adult males (Gobush et al., 2008), poachers also target female matriarchs as they also have large tusks and are easier to find than solitary males (Poole, 1989). Poaching disrupts kin-based association patterns, decreases the quality of elephant social relationships, and increases male reproductive skew, with significant consequences for population health and the maintenance of genetic diversity (Archie & Chiyo, 2012). ...
... Poaching targets large individuals for their higher tusk sizes (Mondol et al., 2014). Although poaching for ivory primarily targets single adult males (Gobush et al., 2008), poachers also target female matriarchs as they also have large tusks and are easier to find than solitary males (Poole, 1989). Selective removal of larger adult males and females from elephant populations affects age and sex structure. ...
... In contrast, most populations of African elephants outside the Serengeti experienced a rapid decline. Populations that have experienced heavy poaching tend to have skewed adult sex ratio in favor of females, (Poole, 1989) lower OSR and a higher proportion of tuskless individuals . Given the fact that the SNP is experiencing the opposite of what is happening in most other areas of Africa, we do not expect the adult sex ratio to deviate significantly from 1:1. ...
Thesis
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African savanna elephants (Loxodonta africana) are ecologically important as ecosystem engineers and socio-politically as revenue earners for national economies and local communities. However, their population has declined due to poaching and loss of habitat as a result of an increase in the human population. Habitat loss and fragmentation makes most protected areas isolated because of blocking of wildlife corridors. This study covered four ecosystems (Serengeti, Tarangire-Manyara, Selous, and Ruaha) in Tanzania which have the largest elephant populations in the country to determine the extent of genetic diversity and population structure nuclear and mitochondrial DNA markers. We wanted to establish historical genetic connectivity using mitochondrial DNA and contemporary gene flow using microsatellite markers from DNA obtained non-invasively from fecal samples. We specifically wanted to determine if there is gene flow between the Serengeti and Tarangire-Manyara ecosystems and whether the genetic structure has substantially changed over the past 50 years. We assumed that the Greater Rift Valley between two ecosystems would also act a barrier to the gene flow. We collected 800 elephant fecal samples from the four ecosystems and performed genetic analyses at the Pennsylvania State University. Our results showed that the Serengeti elephants are genetically distinct from the Tarangire-Manyara. Elephants from Ngorongoro showed an admixture between the two ecosystems. We also identified that there was a higher genetic similarity of elephants between Ngorongoro and Lake Manyara compared to Lake Manyara and Tarangire. Also, Tarangire and Ruaha elephants shared the same population structure although they are more than 400 km apart. Within the Serengeti ecosystem, we identified two population clusters from south and north of the Serengeti. Our results suggest that even without any physical barriers, there is genetic differentiation. The analysis of nuclear and mitochondrial DNA showed significant population differentiation between the Ruaha and Selous ecosystems. We further found no evidence for female-mediated gene flow between Ruaha and Selous. Only 4% of elephants sampled in Ruaha shared a haplotype with the Selous Game Reserve.We also developed a novel fecal-centric approach to assess the age and sex structure of elephants and validated it with a rapid demographic assessment. We compared the sex ratio of elephants between Serengeti National Park, Ngorongoro Conservation Area and Maswa Game Reserve which have different protection status. In Serengeti, the sex ratio for adult age classes was skewed in favor of females whereas, in Ngorongoro, the sex ratio was skewed in favor of males for elephants older than 25 years. Although poaching is the main explanation for the observed sex ratio in Serengeti, we speculate that differential survival rates between males and female could explain the differences in sex ratio, particularly for young elephants. Our findings provide baseline information about historical connectivity using the mitochondrial DNA and recent gene flow (using nuclear markers) between protected areas in Tanzania. This information may be used to inform laws to protect the existing wildlife corridors or to restore the blocked corridors. We have highlighted some wildlife corridors that may have been or are still very important for the elephants based on our data; these would be suitable targets for conservation and restorations
... Moreover, family groups occupy areas beyond the confines of wildlife preserves all across the African continent [16,17,22,25]. These factors drive musth males to travel farther, faster, and with more directional purposes [11,[26][27][28][29][30]. As a result, elephants that are sexually active or in musth may enter unprotected areas adjacent to wildlife parks where human-elephant conflict (HEC) continues to intensify [20,31,32]. ...
... Adult female elephants only enter into estrus every four-five years due to lengthy gestational and postpartum lactation periods that prolong inter-calving intervals [12,58,59]. Moreover, peak estrus in female African elephants only lasts two-three days [27,60], making it imperative that males recognize a female's reproductive status and locate her across vast landscapes. To signal their reproductive status and attract males, estrous females engage in distinctive behaviors [58], emit characteristic estrous roars when chased [61] and, during peak estrus, produce a series of low-frequency estrous rumbles immediately after mating [27,30,52,62]. ...
... Moreover, peak estrus in female African elephants only lasts two-three days [27,60], making it imperative that males recognize a female's reproductive status and locate her across vast landscapes. To signal their reproductive status and attract males, estrous females engage in distinctive behaviors [58], emit characteristic estrous roars when chased [61] and, during peak estrus, produce a series of low-frequency estrous rumbles immediately after mating [27,30,52,62]. These low-frequency estrous calls can propagate on the order of several kilometers and are likely to be heard by many elephants [56,63]. ...
Article
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Driven by reproductive motives, male African elephants (Loxodonta africana) in musth often expand their home ranges to locate estrous females. This extended range, coupled with heightened aggression often observed in musth males, can be particularly problematic in regions where human-modified landscapes and elephant territories increasingly overlap. Several mitigation tools have been tested to resolve a wide range of human–elephant conflicts with varying degrees of success due to geographical disparities and habituation. We present findings on the potential application of estrous call playbacks in manipulating the behavior and movement of male elephants non-invasively, particularly mature musth adults and younger post-dispersal males, in Etosha National Park. Estrous vocalizations were presented across 26 experimental trials to mature musth adults (n = 5), mature non-musth adults (n = 6), and non-musth males belonging to younger, post-dispersal age classes (n = 8), with behavioral responses scored on a gradient scale from 0–1. Both mature musth adults and younger non-musth elephants were significantly more likely to respond with the highest intensity by approaching the acoustic source compared to mature non-musth adults that avoided the call. However, younger males tested in the presence of an older, higher-ranking male tended to react with a lower intensity than those tested alone. This result likely demonstrates the influence of social hierarchy and associations on male elephant behavior. We also observed a significant increase in physiological response, measured by defecation rate, across all male groups in response to the estrous call playbacks. Our findings suggest that using estrous calls as acoustic deterrents may effectively and non-invasively aid in reducing tension at the human–elephant interface, depending on the age, social context, and reproductive status of the male elephant.
... There is preliminary genetic evidence that dispersal is not random, and groups of adolescent bulls are related to one another (Vidya & Sukumar, 2005;Chiyo et al., 2011). Greeting and sparring with similar-aged males, both familiar and unknown, enables an individual bull to assess his position in the hierarchy, develop social skills and gain knowledge about possible future opponents with whom he will compete for access to females (Poole, 1989;Beacham, 2003;Evans & Harris, 2008). Adolescents also associate with older bulls, presumably to gain knowledge about the environment, the location of forage, and to learn appropriate social and reproductive behaviours (Rees, 2004;Chiyo et al., 2011;Goldenberg et al., 2014). ...
... The phenomenon of musth is unique to bull elephants; it is a period of intense sexual activity characterized by high testosterone levels, urine dribbling and temporal-gland secretion (Poole & Moss, 1981;Poole, 1987). Musth confers a breeding advantage to sexually mature bulls: oestrous females select musth bulls as mating partners and mating success increases after males have experienced their first period of musth (Poole, 1989;Hollister-Smith et al., 2007). During musth, gonadally derived testosterone, and its physiologically active metabolite dihydrotestosterone, increase dramatically, often rising tenfold or more above baseline levels (Yon et al., 2007). ...
... Bulls come into musth asynchronously (Poole, 1987) and each bull has his own annual musth cycle. This has the added benefit that potential conflict between bulls is avoided, as bulls in musth will suppress other bulls both socially and sexually (Poole, 1989;Slotow et al., 2000;Evans & Harris, 2008;Wyse et al., 2017). Musth bulls display a wide range of physical, acoustic, olfactory, chemical and behavioural signals to communicate their status to cows as well as to other bulls (Poole & Moss, 1981;Vidya & Sukumar, 2005), and often show aggressive behaviour, both to conspecifics and to other animals in the landscape (Poole, 1989). ...
Article
In the wild, bull elephants socialize with conspecifics of all ages and both sexes, and young bulls develop social bonds with other elephants which will be sustained throughout their lives. Significant progress has been made towards providing an environment that facilitates social behaviour and multi‐generational family structure for female elephants in zoos. However, it is more complex and challenging to build facilities and manage groups of elephants in ways that allow fission–fusion herd dynamics and give the elephants choice over their environment. For bulls, this is further complicated by their potential strength and aggressive behaviour. To advance the development of best‐practice management for zoo elephants and achieve high standards of welfare, it is necessary to improve our understanding of the social and behavioural needs of bull elephants, and implement radical and innovative solutions to their care. In this paper we (1) consider how the social behaviour of bull elephants is addressed in zoos, comparing their social management with their behaviour in the wild, (2) contribute novel preliminary data about how these issues are addressed, and (3) propose some new approaches to the management of bull elephants in zoos for the future. Bull elephants socialize with conspecifics of all ages and both sexes; and young bulls develop social bonds with other elephants that will be sustained throughout their lives. However, it is complex and challenging in zoos to build facilities and manage groups of elephants in ways that allow fission–fusion herd dynamics and give the elephants choice over their environment. To advance the development of best‐practice management for zoo elephants it is necessary to improve our understanding of the social and behavioural needs of bull elephants, and implement innovative solutions to their care. This paper considers the social behaviour of bull elephants, contributes novel preliminary data about how these issues are addressed and proposes some new approaches to the management of bull elephants in zoos. (Photo: Lisa Yon, University of Nottingham)
... 6 [53][54][55][56][57][58] 8.8.2 Inspectors, local authorities and zoos should also consult the current Management Guidelines for the Welfare of Zoo Animals: Elephants (BIAZA). Elephant-keeping zoos must engage constructively with the Elephant Welfare Group (administered by BIAZA), which may include assisting with monitoring and recording welfare and other parameters, to help the Group monitor progress in the national herd. ...
... Wild African elephant literature : social learning, bull social mixing with family herds 9 [54,55,57,79,[85][86][87]103,104] ' Bulls in bachelor herds' ...
... 3 [49,59,63] 11 [61,[64][65][66][67][68][69][70][71][72][73] 10 ' Herd with a wide range of ages' 4 [61,[74][75][76] 9.0 Wild African elephant literature : social learning, bull social mixing with family herds 9 [54,55,57,79,[85][86][87]103,104] Enclosures 8.8.8 Indoor and outdoor accommodation must be provided and other than in exceptional weather conditions, elephants should have access to both over a 24 hour period and be able to choose where they spend their time. ...
Research
Full-text available
A novel tool was created to assess the welfare of captive elephants using behavioural indicators of welfare. The tool was designed for use by elephant keepers to provide a rapid, reliable and valid way to monitor changes in the welfare of elephants over time. A detailed and extensively evidence-based review was made of the Secretary of State Standards of Modern Zoo Practice (SSSMZP) guidelines on keeping elephants. This evidence was reviewed by experts, who made suggestions for revisions to the current guidelines.
... However, similar to any other sexually selected trait, the occurrence of musth should be linked to variation in reproductive success (Hosken & House, 2011). Elephants are polygynous and do not defend distinct territories, nor do adult male elephants typically associate with females beyond the period of oestrus (Poole, 1989b;Ganswindt et al., 2005b;Vidya & Sukumar, 2005;de Silva & Wittemyer, 2012). Therefore, it is unlikely that females choose to mate with musth males as a result of a direct benefit, such as parental care, protection, or access to resources within a territory (Møller & Jennions, 2001;Jones & Ratterman, 2009). ...
... Females preferentially associate with musth males, which leads to more successful mating attempts by these males (Poole, 1989b;Chelliah & Sukumar, 2015). In long-lived species with prolonged interbirth intervals, only long-term studies can answer if these intersexual associations and mating attempts lead to increased paternity success . ...
... However, given the continued controversy of the Handicap Principle in its varied forms (Penn & Számadó, 2020), a re-evaluation of musth in a Darwinian framework would be valuable. From musth's first scientific descriptions, biologists have hypothesised about its value to female mate choice (Eisenberg et al., 1971;Eisenberg, 1980;Hall-Martin, 1987;Poole, 1989b), and the process of mate choice is critical for intersexual selection to occur. Sexual selection theory posits that the selection for sexual traits (such as musth) results from the balance between a mating advantage and increased risk of mortality. ...
Article
Full-text available
Sexual selection mediated by multimodal signals is common among polygynous species, including seasonally breeding mammals. Indirect benefit models provide plausible explanations for how and why mate selection can occur in the absence of direct benefits. Musth-an asynchronous reproductive state in male elephants-facilitates both inter-and intrasexual selection via indirect benefits, and it is further communicated through a multimodal signal. In this review, we synthesise existing evidence that supports the hypothesis that musth is a multimodal signal subject to sexual selection and that male elephants increase their direct fitness by propagating this signal while females accrue indirect benefits. Musth is characterised by a suite of physiological and behavioural changes, serving to facilitate copulation between the sexes, and via multisensory modalities musth conveys honest information about the condition of a male. Female elephants mate preferentially with musth males, increasing their own fitness in the absence of direct benefits. In addition, musth resolves dynamic dominance hierarchies among male elephants and often eliminates the need for costly physical combat. Future work in this field should investigate potential postcopulatory selection mechanisms in elephants, including sperm competition and cryptic female choice. These topics join other fundamental questions related to sexual selection, signalling, and indirect benefits that are still unanswered in elephants.
... Musth is a physiological and behavioral phenomenon characterized by increased testosterone, heightened aggression or unpredictability, increased sexual behavior, and a temporary rise in dominance in both wild and captive Asian [1][2][3][4][5] and African [1,[6][7][8][9][10] elephant bulls. Bulls advertise musth status through a variety of chemicals exuded in temporal gland secretions and urine [5,[11][12][13], and secretions from the paired facial temporal glands and dribbling of urine from the penile prepuce characterize physical signs of musth [3,5,6,8,9,11,12,14,15] which are also visible. ...
... The youngest male showed increased testosterone with age in the 5 years after his first musth cycle, and then a gradual decrease. In younger males, expression of musth is shorter and more sporadic, becoming more robust with increasing age [4,6,10,11]. All older bulls showed decreased mean testosterone past 31-40 years of age, providing evidence of age-related decreases in testosterone similar to those found in male model species [64] and humans [65,66]. ...
Article
Full-text available
The conservation of endangered species and sustainability of managed populations requires considerations to ensure the health and welfare of individuals. Male elephants experience a biological phenomenon called “musth”, which is characterized by increased testosterone production, temporal gland secretion and urine dribbling, heightened aggression and sexual behavior, and therefore can pose unique challenges for human safety and animal welfare. This study characterized longitudinal (9 to 22 years) patterns of circulating testosterone and cortisol in relation to musth in four adult Asian elephant bulls spanning ages from 12 to 54 years. Age-related effects on musth activity and adrenal responses to social changes and clinical health events were also examined. All bulls exhibited regular annual musth cycles. Circulating cortisol covaried positively with testosterone and musth, highlighting intrinsic patterns that should be considered when evaluating the impact of social, health, and environmental changes on adrenal glucocorticoid activity. Except for an end-of-life cortisol increase in one bull, there was no clear evidence of chronically elevated cortisol secretion outside of musth in any individual. Testosterone decreased with age in sexually mature bulls, whereas age-related changes in cortisol varied across individuals, with the three older bulls showing the greatest rate of change during musth versus inter-musth periods. In contrast to physiological factors, there was no evidence of social factors, such as addition of a new male and death of male herdmates, impacting adrenal glucocorticoid activity in these bulls in the short term. Changes in cortisol were associated with treatment for Mycobacterium tuberculosis (M. tb) in two bulls, increasing after start of treatment and decreasing with cessation of treatment, but were not clearly associated with activation of disease. This study highlights the importance of longitudinal hormone monitoring to track changes in physiological function and responses to social, health, and environmental change in elephant bulls, which is important for making more informed decisions on how to manage male elephants under varying degrees of human care to ensure welfare and safety.
... If access to unrelated females is important, the initial gradual locational dispersal of males would allow young males to achieve this , while musth might facilitate older males to encounter more unrelated females through roving behavior. In African savannah elephants (Poole 1989b) and another population of Asian elephants (Chelliah and Sukumar 2015), female elephants were observed to prefer musth males, rather than non-musth males, as mates. We cannot rule out the possibility that, while musth serves as a roving or mate searching strategy for old males, it may simultaneously provide some advantage to young males in terms of female choice if they encounter a receptive female. ...
... Male African savannah elephants have been thought to have a distinct non-musth, sexually active period (Ganswindt et al. 2005;Rasmussen et al. 2008a), during which they associate to a greater extent with female groups and have higher levels of testosterone compared with sexually inactive males. Young males also have been shown to employ alternate reproductive tactics such as sneak mating while not in musth, with some moderate success (see Poole 1989b;Hollister-Smith et al. 2007;Rasmussen et al. 2008b;Poole et al. 2011). There are no distinct locations in our study area that could result in clearly separated spaces for sexually inactive and active males, and we have not observed distinct sexually active and inactive non-musth states. ...
Article
Musth is an annual, asynchronous, rut-like phenomenon observed in male elephants. We examined whether musth is a roving strategy, and whether musth provides a temporary advantage to young males through increased access to female groups. We collected long-term data on the musth status, associations, and locations of male elephants in the Kabini population in southern India. We sighted older males more frequently in musth than younger males. We found a greater turnover of musth than non-musth males in the study area, suggesting that musth is a roving strategy, enabling males to travel widely and away from their non-musth range. Contrary to our expectation, young (15–30 years old) males spent a smaller proportion of their musth time than their non-musth time associating with females, and associated with similarly sized female groups irrespective of musth status. Old (> 30 years old) males spent only a slightly higher proportion of their musth time than non-musth time with female groups, but associated with larger female groups during musth. Although old males in musth associated with young non-musth males more often in the presence, than in the absence, of females, young males in musth were never sighted with old non-musth males in the presence of females. Therefore, the payoff from musth, as a strategy to gain access to females, was age-specific; musth in old males allowed for increased association with females, while musth in young males restricted their access to females. There was no spatial avoidance between musth and non-musth adult males at scales larger than immediate associations. Our results suggest that musth seems to be primarily a roving strategy for old males to find and associate with females and not a strategy for young males to gain a temporary advantage over old males, within the broad age-classes that we examined.
... If access to unrelated females is important, the initial gradual locational dispersal of males would allow young males to achieve this , while musth might facilitate older males to encounter more unrelated females through roving behavior. In African savannah elephants (Poole 1989b) and another population of Asian elephants (Chelliah and Sukumar 2015), female elephants were observed to prefer musth males, rather than non-musth males, as mates. We cannot rule out the possibility that, while musth serves as a roving or mate searching strategy for old males, it may simultaneously provide some advantage to young males in terms of female choice if they encounter a receptive female. ...
... Male African savannah elephants have been thought to have a distinct non-musth, sexually active period (Ganswindt et al. 2005;Rasmussen et al. 2008a), during which they associate to a greater extent with female groups and have higher levels of testosterone compared with sexually inactive males. Young males also have been shown to employ alternate reproductive tactics such as sneak mating while not in musth, with some moderate success (see Poole 1989b;Hollister-Smith et al. 2007;Rasmussen et al. 2008b;Poole et al. 2011). There are no distinct locations in our study area that could result in clearly separated spaces for sexually inactive and active males, and we have not observed distinct sexually active and inactive non-musth states. ...
Preprint
We present here, the first detailed study of adult male associations in an Asian elephant population, using six years of data collected on identified males. As expected in a large, polygynous species, adult males spent greater proportions of their time solitarily or in mixed-sex groups than in all-male groups. However, the adult male associations seen were complex, with different patterns of male associations based on their age and on the presence or absence of females. Old and young males spent more time associating with their age-peers and less time associating across age classes than expected at random in the absence of females. Young males did not spend a greater proportion of their time with old males than with young males. Young males did not initiate associations with old males to a greater extent than old males approaching young males. Moreover, male age was not correlated with centrality measures in association networks and was negatively correlated with the number of unique associates per time in the absence of females. All of these suggest that male associations in female absence are primarily a means for males to test strengths against age-peers rather than an opportunity for social learning from old males. Male associations in female presence were rarer than in female absence, and old, reproductively competitive, males avoided each other in female presence, resulting in different male association network properties. Although male associations were generally weak and not stable across years, there were some significant associations. Overall, there was a smaller proportion of time spent in all-male groups, smaller group sizes, and a limited role of older males in the association network in the Kabini Asian elephant population compared to the phylogenetically closely related African savannah elephant. These differences may be related to differences in resource distributions in the two habitats.
... On occasion, other adult females and juveniles guard or instruct calves, reflecting the highly social and cohesive nature of elephant families . Unlike the social-group-living females, pubertal males disperse from their natal family at an average age of 14 Poole, 1989). African and Asian elephants exhibit a polygynous mating system, in which adolescent males are known to associate with other bulls, depending on their age and sexual state, and may rove between female groups throughout the year to temporarily associate and start competing with one another over receptive females (Eisenberg et al., 1971;Moss & Poole, 1983;Poole, 1989). ...
... Unlike the social-group-living females, pubertal males disperse from their natal family at an average age of 14 Poole, 1989). African and Asian elephants exhibit a polygynous mating system, in which adolescent males are known to associate with other bulls, depending on their age and sexual state, and may rove between female groups throughout the year to temporarily associate and start competing with one another over receptive females (Eisenberg et al., 1971;Moss & Poole, 1983;Poole, 1989). ...
Article
Full-text available
Vocal production learning is the ability to modify a vocal output in response to auditory experience. It is essential for human speech production and language acquisition. Vocal learning evolved independently several times in vertebrates, indicating evolutionary pressure in favor of this trait. This enables cross-species comparative analysis to be used to test evolutionary hypotheses. Humans share this ability with a versatile but limited group of species: songbirds, parrots and hummingbirds, bats, cetaceans, seals, and elephants. Although case studies demonstrate that African savanna and Asian elephants are capable of heterospecific imitation, including imitation of human words, our understanding of both the underlying mechanisms and the adaptive relevance within the elephant’s natural communication system is limited. Even though comparing phylogenetically distant species is intriguing, it is also worthwhile to investigate whether and to what extent learned vocal behavior is apparent in species phylogenetically close to an established vocal learner. For elephants, this entails determining whether their living relatives share their special ability for (complex) vocal learning. In this review, we address vocal learning in Elephantidea and Sirenia, sister groups within the Paenungulata. So far, no research has been done on vocal learning in Sirenians. Because of their aquatic lifestyle, vocalization structure, and evolutionary relationship to elephants, we believe Sirenians are a particularly interesting group to study. This review covers the most important acoustic aspects related to vocal learning in elephants, manatees, and dugongs, as well as knowledge gaps that must be filled for one to fully comprehend why vocal learning evolved (or did not) in these distinctive but phylogenetically related taxa.
... Rare bird species such as Hubara bustard are under severe pressure and extinction. The phonological effect of CC will also impact the seasons for bird migration [128]. Some mammalian species such as rodents could also be affected in terms of population dynamics and distribution. ...
... This may increase conflicts between people and large mammals such as elephants, particularly in areas where rainfall is low [129]. Subsequently, change in the intensity and duration of the rainy vs. dry seasons could change breeding rates and genetic structures in those populations [128]. ...
Article
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Climate change is happening due to natural factors and human activities. It expressively alters biodiversity, agricultural production, and food security. Mainly, narrowly adapted and endemic species are under extinction. Accordingly, concerns over species extinction are warranted as it provides food for all life forms and primary health care for more than 60–80% of humans globally. Nevertheless, the impact of climate change on biodiversity and food security has been recognized, little is explored compared to the magnitude of the problem globally. Therefore, the objectives of this review are to identify, appraise, and synthesize the link between climate change, biodiversity, and food security. Data, climatic models, emission, migration, and extinction scenarios, and outputs from previous publications were used. Due to climate change, distributions of species have shifted to higher elevations at a median rate of 11.0 m and 16.9 km per decade to higher latitudes. Accordingly, extinction rates of 1103 species under migration scenarios, provide 21–23% with unlimited migration and 38–52% with no migration. When an environmental variation occurs on a timescale shorter than the life of the plant any response could be in terms of a plastic phenotype. However, phenotypic plasticity could buffer species against the long-term effects of climate change. Furthermore, climate change affects food security particularly in communities and locations that depend on rain-fed agriculture. Crops and plants have thresholds beyond which growth and yield are compromised. Accordingly, agricultural yields in Africa alone could be decline by more than 30% in 2050. Therefore, solving food shortages through bringing extra land into agriculture and exploiting new fish stocks is a costly solution, when protecting biodiversity is given priority. Therefore, mitigating food waste, compensating food-insecure people conserving biodiversity, effective use of genetic resources, and traditional ecological knowledge could decrease further biodiversity loss, and meet food security under climate change scenarios. However, achieving food security under such scenario requires strong policies, releasing high-yielding stress resistant varieties, developing climate resilient irrigation structures, and agriculture. Therefore, degraded land restoration, land use changes, use of bio-energy, sustainable forest management, and community based biodiversity conservation are recommended to mitigate climate change impacts.
... Mate guarding behaviour has evolved in response to male competition in diverse groups (e.g. [10][11][12][13][14]). It is also prevalent among insects [15] and well-studied in the Orthoptera, with males being shown to defend females from other suitors [16], or predators [17], or to defend their own nuptial gifts from removal by the female [18], or scavengers [19]. ...
Article
Full-text available
Mate guarding is a widespread behaviour resulting from sperm competition and conflict over optimal remating rates. It is a key way in which males exhibit differential mating investment, and represents a complex interplay between mating effort, intrasexual competition, opportunity costs and sexual conflict. Nevertheless, although there are many examples of exaggerated male structures used to fight rivals, few animals have developed specialized male morphological adaptations for directly sheltering females from disturbance by non-rivals. Here we report on the use of sexually dimorphic, elongated male hind legs, which are used to guard females in the New Zealand cave wētā Pachyrhamma waitomoensis (Orthoptera: Rhaphidophoridae). We found that male hind legs alongside the female failed to deter rivals from accessing her or disrupting copulation. However, they did reduce the disturbance to females from other, non-rival animals such as juveniles and heterospecifics. Males with longer hind legs were more effective in reducing disturbance, and remained with females for longer. Longer guarding periods also led to higher numbers of matings between pairs. Models of males with artificially altered hind leg dimensions also showed a benefit to greater leg length, and artificially altering the disturbance rate to females also had a significant effect on pair duration. Our results indicate that nuisance disturbance to females may play an important role in driving sexual selection on male leg length and its exaggeration in this species.
... We propose to address these questions using two complementary areas of research: the study of elephant behavior and cognition, and the study of elephant ecology and life history. Studies conducted both in Africa and Asia, with both captive and wild populations, show clear evidence for individual differences in a number of ecological and cognitive categories, including parasite load (Lynsdale et al., 2017), body size (Evans and Harris, 2012;Chapman et al., 2016), primiparity (Crawley et al., 2017), social hierarchy (McComb et al., 2011), innovation (Bates et al., 2008b), cooperation (Plotnik et al., 2011), problem-solving (Foerder et al., 2011), aggression (Poole, 1989), and personality (Lee and Moss, 2012;Yasui et al., 2012;Seltmann et al., 2018). Identifying whether or not specific behavioral, physical, demographic or personality traits (collected through future ecological, ethological and experimental research on captive and wild elephants) correlate with an elephant's propensity to crop-raid or engage in conflict may have important implications for preventing or managing these conflicts across different landscapes. ...
Article
Full-text available
Conflict between humans and wildlife is an increasing problem worldwide due to human population growth and habitat fragmentation, with growing interest amongst scientists and conservationists in developing novel solutions toward sustainable coexistence. Current efforts to mitigate human–wildlife conflict, however, are often unbalanced; they consider immediate human-centric concerns and offer deterrents against wildlife, rather than offering solutions to the underlying problems. Recently, there has been an increase in the number of calls to action for the integration of animal behavior, cognition and knowledge of individual variation into conservation practice. However, as elephant researchers, we have seen that most human–elephant conflict mitigation strategies employed in Asia and Africa are based on conditioning fear in elephants, or general monitoring of individual or group activities aimed at altering elephant movements, rather than understanding and providing for elephant and human needs. We see an opportunity to do more by investigating elephant behavior, cognition and ecology at the level of the individual to prevent conflict from occurring in the first place. Here, we review studies on elephants to illustrate this concept and to outline avenues for the application of research on elephant ecology, life history, behavior and personality to the development of new, comprehensive conservation strategies that take both human and elephant behavior into account.
... Despite the increase in faecal glucocorticoid metabolites, the stress response in elephants was short-lived and, in our opinion, not detrimental (the peaks being lower than that shown to natural extreme stressors such as transport or extreme, loud, noises including thunderstorms [9]). However, bulls should preferably not be hunted when they are in musth as they are more aggressive and unpredictable than usual [31,32]. Because of observed stress responses of bulls present at the hunt, best practice to reduce unnecessary stress indicates that bulls should only be hunted when they are alone. ...
Chapter
Background Hunting of male African elephants may pose ethical and risk concerns, particularly given their status as a charismatic species of high touristic value, yet which are capable of both killing people and damaging infrastructure.Methodology/Principal Findings We quantified the effect of hunts of male elephants on (1) risk of attack or damage (11 hunts), and (2) behavioral (movement dynamics) and physiological (stress hormone metabolite concentrations) responses (4 hunts) in Pilanesberg National Park. For eleven hunts, there were no subsequent attacks on people or infrastructure, and elephants did not break out of the fenced reserve. For three focal hunts, there was an initial flight response by bulls present at the hunting site, but their movements stabilised the day after the hunt event. Animals not present at the hunt (both bulls and herds) did not show movement responses. Physiologically, hunting elephant bulls increased faecal stress hormone levels (corticosterone metabolites) in both those bulls that were present at the hunts (for up to four days post-hunt) and in the broader bull and breeding herd population (for up to one month post-hunt). Conclusions/Significance As all responses were relatively minor, hunting male elephants is ethically acceptable when considering effects on the remaining elephant population; however bulls should be hunted when alone. Hunting is feasible in relatively small enclosed reserves without major risk of attack, damage, or breakout. Physiological stress assays were more effective than behavioral responses in detecting effects of human intervention. Similar studies should evaluate intervention consequences, inform and improve best practice, and should be widely applied by management agencies.
... Musth is similar to rutting behaviour in ungulates and is associated with periodic increases of testosterone secretion. Most matings occur in this period (Poole, 1989). During musth, the animal becomes more restless, energetic, aggressive and generally irritable and oversensitive to sound and movements. ...
... Elephants are one of the few animals whose reproductive fitness increases with age, which may have selected for their effective cancer-suppression mechanisms (Poole, 1989;Abegglen et al., 2015). ...
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Cancer is a disease of multicellularity; it originates when cells become dysregulated due to mutations and grow out of control, invading other tissues and provoking discomfort, disability, and eventually death. Human life expectancy has greatly increased in the last two centuries, and consequently so has the incidence of cancer. However, how cancer patterns in humans compare to those of other species remains largely unknown. In this review, we search for clues about cancer and its evolutionary underpinnings across the tree of life. We discuss data from a wide range of species, drawing comparisons with humans when adequate, and interpret our findings from an evolutionary perspective. We conclude that certain cancers are uniquely common in humans, such as lung, prostate, and testicular cancer; while others are common across many species. Lymphomas appear in almost every animal analysed, including in young animals, which may be related to pathogens imposing selection on the immune system. Cancers unique to humans may be due to our modern environment or may be evolutionary accidents: random events in the evolution of our species. Finally, we find that cancer‐resistant animals such as whales and mole‐rats have evolved cellular mechanisms that help them avoid neoplasia, and we argue that there are multiple natural routes to cancer resistance.
... Since the rainfall pattern for RCP 2. In terms of breeding and genetics a change in the intensity or duration of the rainy versus drought seasons could change relative breeding rates and, hence, genetic structures in these populations [79] [84]. Therefore increased rains in the OND season will have a positive impact on the elephant population of Amboseli ecosystem but work on elephant population dynamics is needed (refer to [49] [88] As indicated in this study that it is projected there is likely possibilities of increase in elephant population based on all the three RCPs 2.6, 4.5 and 8.5 in the Amboseli ecosystem which could boost tourism activities in the area. ...
... Sperm competition is a form of male-male competition, but since the sperm of two or more males compete to fertilize the ova, it can also have direct implications in intrasexual interactions (Parker, 1970). Males have evolved an array of strategies to establish final precedence of their sperm by enforcing female monogamy (Gillies 1956, Gilbert 1976, Ehrlich and Ehrlich 1978, Sillén-Tullberg 1981, Thornhill and Alcock 1983, Svard and Wiklund 1988, Dickinson and Rutowski 1989, Poole 1989, Mclain 1989, Matsumoto and Suzuki 1995, Orr 1995, Orr 1999, Sauter et al. 2001, Dixson and Anderson 2002, Schulz et al. 2008, Timmermeyer et al. 2010, Uhl et al. 2010, Carvalho et al. 2017, Malouines 2017, and any male that prevents a female from remating will be in direct conflict with her if the female would otherwise benefit from remating. This intersexual conflict can trigger sexually antagonistic coevolution (Rice 1996), where adaptations evolve in one sex in order to increase its fitness, which will result in lower fitness for the opposite sex. ...
Article
Sexual reproduction is often associated with intra- and intersexual conflict, especially in species where females mate multiple times. A strategy that has evolved in males to ensure offspring paternity is the ability to produce a complex, external mating plug called a sphragis. The sphragis has been found in 273 butterfly species; however, little is known about the sphragides of the butterflies in the nymphalid genus Pteronymia. In this study, we describe the sphragides of all sphragis-bearing species in Pteronymia, including the newly discovered sphragides of P. alissa (Hewitson), P. andreas (Weeks), P. ozia (Hewitson), and P. zerlina (Hewitson). Three additional species, P. fulvimargo Butler & Druce, P. oneida (Hewitson), and P. ticida (Hewitson), are found to bear an irregular sphragis-like structure. We use molecular and morphological data from a recent study to construct a phylogeny of species in the genus and examine the number of independent origins of the sphragis. Our ancestral state reconstruction using Bayesian inference suggests that the sphragis evolved three times in Pteronymia, whereas parsimony character optimization performed on a maximum likelihood tree suggests only one origin of this structure. Our data on ancestral state patterns, frequency of incomplete sphragides, and morphology of female external genitalia suggest that sphragis-bearing Pteronymia may be in active intersexual conflict, where females develop strategies to prevent male plugging.
... Higher Aggressiveness in male elephants might be explained by their need to assess each other's dominance status by less-aggressive sparring bouts or by more-aggressive interactions during musth 14 . The Aggressiveness personality trait is related to ratings of aggressive, moody, and dominant behaviour 11 (Fig. 1), and higher aggression has a crucial impact in maximising reproductive success in male elephants as older larger and more aggressive males are more successful in mate guarding than less aggressive males 33 . ...
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Personality, i.e. consistent between-individual differences in behaviour, has been documented in many species. Yet little is known about how males and females of long-lived, highly social species differ in their measures of personality structure. We investigated sex differences in the mean, variance, and covariance of three previously reported personality traits (Attentiveness, Sociability, Aggressiveness) in 150 female and 107 male Asian elephants (Elephas maximus) from a semi-captive population in Myanmar. These three personality traits were obtained by performing exploratory factor analysis on 28 behavioural items that had been rated by experienced elephant handlers. We found that males scored significantly higher on Aggressiveness and tended to score lower on Sociability than females. However, no sex difference was found in the mean scores of Attentiveness. Variances for the three personality traits did not differ between the sexes, suggesting that male and female elephants share the same range of personality variation. Likewise, trait covariances were similar between the sexes. While both sexes show complex sociality in the wild, female Asian elephants typically live in highly social family units, whereas male elephants’ social bonds are weaker. Males usually form dominance ranks by aggressive interactions, especially during musth. Our results on a large sample of individuals living in their natural environment are thus in agreement with elephant life-histories and parallel the findings of sex differences in other long-lived highly social species with similar life-histories.
... Musth is similar to rutting behaviour in ungulates and is associated with periodic increases of testosterone secretion. Most matings occur in this period (Poole, 1989). During musth, the animal becomes more restless, energetic, aggressive and generally irritable and oversensitive to sound and movements. ...
... Musth duration and regularity is positively related to age, with males over 35 displaying regular musth periods once a year for an extended duration (~2 months), whilst younger bulls between ~26 and 35 tend to express musth characteristics for up to 2 weeks several times a year (Poole, 1987;Poole, Lee, Njiraini, & Moss, 2011). Thus, the reproductive success of a male elephant increases with age, both through reductions in intrasexual competition by the escalation of size-related dominance (Poole, 1989a), and an increase in intersexual selection by females for older males (Moss, 1983;Poole, 1989b). However, despite the reproductive dominance of older males, younger males still contribute to the gene pool (Hollister-Smith et al., 2007;Rasmussen, Okello, et al., 2008). ...
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Long‐term bio‐logging has the potential to reveal how movements, and hence life‐history trade‐offs, vary over a lifetime. Reproductive tactics in particular may vary as individuals' trade‐off current investment versus lifetime fitness. Male African savanna elephants (Loxodona africana) provide a telling example of balancing body growth with reproductive fitness due to the combination of indeterminate growth and strongly delineated periods of sexual activity (musth), which results in reproductive tactics that alter with age. Our study aims to quantify the extent to which male elephants alter their movement patterns, and hence energetic allocation, in relation to (a) reproductive state and (b) age, and (c) to determine whether musth periods can be detected directly from GPS tracking data. We used a combination of GPS tracking data and visual observations of 25 male elephants ranging in age from 20 to 52 years to examine the influence of reproductive state and age on movement. We then used a three‐state hidden Markov model (HMM) to detect musth behaviour in a subset of sequential tracking data. Our results demonstrate that male elephants increased their daily mean speed and range size with age and in musth. Furthermore, non‐musth speed decreased with age, presumably reflecting a shift towards energy acquisition during non‐musth. Thus, despite similar speeds and marginally larger ranges between reproductive states at age 20, by age 50, males were travelling 2.0 times faster in a 3.5 times larger area in musth relative to non‐musth. The distinctiveness of musth periods over age 35 meant the three‐state HMM could automatically detect musth movement with high sensitivity and specificity, but could not for the younger age class. We show that male elephants increased their energetic allocation into reproduction with age as the probability of reproductive success increases. Given that older male elephants tend to be both the target of legal trophy hunting and illegal poaching, man‐made interference could drive fundamental changes in elephant reproductive tactics. Bio‐logging, as our study reveals, has the potential both to quantify mature elephant reproductive tactics remotely and to be used to institute proactive management strategies around the reproductive behaviour of this charismatic keystone species. Combining GPS tracking with visual observations of male elephants, the authors found that older individuals markedly increased their daily speed and range use when reproductively active. Reproductively associated movements were not identifiable for younger individuals. Automatic detection of reproductive state in mature male elephants can be accomplished with GPS tracking.
... An important physiological change that occurs in male elephants during this phase is the onset of musth 17,18 , characterized by enhanced testosterone level and increased sexual activity 13,19 . When in musth, male African and Asian elephants are known to associate with females to mate with them 13,20,21 . Dynamic changes in social associations and behavioural strategies seem to be appearing amongst both female and male elephants, in populations that are living in rapidly changing ecological and anthropogenic environments [21][22][23] . ...
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Male Asian elephants are known to adopt a high-risk high-gain foraging strategy by venturing into agricultural areas and feeding on nutritious crops in order to improve their reproductive fitness. We hypothesised that the high risks to survival posed by increasingly urbanising and often unpredictable production landscapes may necessitate the emergence of behavioural strategies that allow male elephants to persist in such landscapes. Using 1445 photographic records of 248 uniquely identified male Asian elephants over a 23-month period, we show that male Asian elephants display striking emergent behaviour, particularly the formation of stable, long-term all-male groups, typically in non-forested or human-modified and highly fragmented areas. They remained solitary or associated in mixed-sex groups, however, within forested habitats. These novel, large all-male associations, may constitute a unique life history strategy for male elephants in the high-risk but resource-rich production landscapes of southern India. This may be especially true for the adolescent males, which seemed to effectively improve their body condition by increasingly exploiting anthropogenic resources when in all-male groups. This observation further supports our hypothesis that such emergent behaviours are likely to constitute an adaptive strategy for male Asian elephants that may be forced to increasingly confront anthropogenically intrusive environments.
... As suggested, young males tend to leave their natal family around the age of 10 to 15 years old but continue contact with the female herd for several years until he is fully independent (Poole, 1989;Sukumar, 2003;Chakraborty et al, 2014 ). This supports my observation of subadult males (M06 and M18) ...
Article
Elephants (Family Elephantidae) are animals that rely on complex social behavior and organization for survival. The current literature on elephant social organization come from studies in African savannas, an open environment where animals are relatively easy to observe and study. Much less is known, however, about the social behavior of forest elephants, particularly of wild elephants (Elephas maximus) in Southeast Asia. Wild elephants in Malaysian rainforests regularly visit mineral licks to supplement their diet with nutrients and to acquire clay to buffer secondary plant compounds This provides a great opportunity to set up camera traps and regularly observe animals that otherwise would be impossible to study in their natural environment. Thus, the objective of this study is 1) to assess the feasibility of using camera traps to study the social structure of elephants in the wild; 2) to describe their social structure; and 3) to quantify wild Asian elephant patterns of mineral lick usage. Individuals were identified using features on the ears, body and tail, or any other prominent profile; and associations between elephants were recorded. Camera traps were set up at a Sira in the Belum Temenggor Forest Complex from October 2012 till October 2013. Video data were retrieved monthly. In total, we recorded 951 hours of videos representing 165 elephant visits. We were able to identify 55 adult individuals while 21 offspring in the age classes of newborn, infants, and juveniles were unidentified over the course of the study. The identified individuals included 26 female adults, 8 female subadults, 15 male adults and 6 male subadults. Seven female family units and four mother-calf units were identified with a median group size of 6 and 2 individuals, respectively. The results show that forest Asian elephants live in smaller groups than their African savanna counterparts. Among the identified elephants, resident family groups were regularly detected, suggesting that mineral licks are important for the feeding ecology of elephants though the reason is still unclear. This study thus provides a baseline of Asian elephant social structure and mineral lick use in Peninsular Malaysia using camera trapping as a recording technique.
... One argument has been that male-male competition may be in part responsible (Roca et al. , 2007. Reproductive success among savanna elephant males is known to depend on body size and age, mediated by periods of musth in which testosterone increases and males become more aggressive towards other males (Poole 1989;Slotow et al. 2000;Hollister-Smith et al. 2007;Rasmussen et al. 2008). Fullygrown forest elephant males are only half as massive as fully-grown savanna elephant males (Groves et al. 1993;Groves and Grubb 2000a, b). ...
Article
During the last two decades, our understanding of the genetics of African elephant populations has greatly increased. Strong evidence, both morphological and genetic, supports recognition of two African elephant species: the savanna elephant (Loxodonta africana) and the forest elephant (L. cyclotis). Among elephantids, phylogeographic patterns for mitochondrial DNA are highly incongruent with those detected using nuclear DNA markers, and this incongruence is almost certainly due to strongly male-biased geneflow in elephants. As our understanding of elephant population genetics has grown, a number of observations may be considered enigmatic or anomalous. Here, several of these are discussed. (i) There are a number of within-species morphological differences purported to exist among elephants in different geographic regions, which would be difficult to reconcile with the low genetic differentiation among populations. (ii) Forest elephants have a higher effective population size than savanna elephants, with nuclear genetic markers much more diverse in the forest elephants than savanna elephants, yet this finding would need to be reconciled with the life history of the two species. (iii) The savanna and forest elephants hybridize and produce fertile offspring, yet full genome analysis of individuals distant from the hybrid zone suggests that gene flow has been effectively sterilized for atleast ∼500,000 years. (iv) There are unexplored potential ramifications of the unusual mito-nuclear patterns among elephants. These questions are considered in light of highmale and low female dispersal in elephants, higher variance of reproductive success among males than females, and of habitat changes driven by glacial cycles and human activity.
... обобщения свидетельствуют о том, что комплементарность действия двух механизмов-явление характерное, хотя при неодновременном их исследовании противоположная направленность наблюдается существенно чаще ( Hunt et al., 2009). Среди млекопитающих такие работы немногочисленны, а конкретные механизмы остаются малоисследованными ( Moss, 1983;Poole, 1989;Fisher et al., 2003;Setchell, 2005). Для ряда видов грызунов было показано, что самки предпочитают спариваться с доминирующими самцами ( Horn, 1974;Huck, Banks, 1982;Parmigiani et al., 1982;Shapiro, Dewsbury 1986). ...
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2014). Много-численные попытки оценить взаимодействие механизмов полового отбора касались главным образом насекомых, рыб, амфибий и птиц (об-зоры: Wong, Candolin, 2005; Hunt et al., 2009). Ре-зультаты этих исследований при попытке их Половой отбор (Darwin, 1871) традиционно подразделяют на внутриполовой (прямая кон-курентная борьба самцов за самку) и межполо-вой (выбор самкой полового партнера). Между двумя механизмами возможно взаимодействие; межполовой отбор может быть комплементарен действию внутриполового отбора, либо иметь противоположное направление (Qvarnström, Forsgren 1998; Moore A., Moore P., 1999; Sih et al., 2002; Wong, Candolin, 2005). В отношении У хомячка Кэмпбелла исследовали связь результатов выбора сексуально мотивированной сам-кой партнера в парах самцов-сибсов с результатами прямой конкуренции (агрессивного и сек-суального доминирования) этих же самцов за самку. Самцы были отобраны по два из вывод-ка по принципу наибольшего различия в экспрессии внешних, связанных с полом признаков (ВПП: масса тела, срединная брюшная железа, ано-генитальное расстояние, средний (из двух бóльших) диаметр семенника по внешним очертаниям). Результаты экспериментов свидетель-ствуют об отсутствии сопряженности у хомячка Кэмпбелла результатов выбора полового пар-тнера самкой с конкурентоспособностью самца, оцененной по уровню агрессивности при сса-живаниях самцов и по уровню сексуальной активности их при свободной конкуренции за самку. Успех самца не был сопряжен с большей экспрессией у него ВПП ни при выборе партне-ра самкой (самцы-сибсы на поводках), ни при ссаживании с самцом-сибсом, ни при свобод-ном доступе самцов к рецептивной самке. Среди самцов с более развитыми ВПП выбор сам-кой партнера не был сопряжен с агрессивным доминированием самца при ссаживании самцов и с сексуальным доминированием самца при свободном доступе самцов к самке. Значимые от-личия по большинству признаков между успешными и неуспешными самцами отсутствовали как при выборе партнера самкой, так и в тестах ссаживания, моделировавших ситуацию кон-куренции самцов. Выявленные с помощью обобщенного регрессионного анализа (GRM) пере-менные, объясняющие выбор партнера самкой и статус самца по уровню агрессивности в пар-ных конфликтах самцов, также не совпадали. Полученный результат не дает повода обсуждать экспрессию ВПП у самцов хомячка Кэмпбелла с позиции взаимодействия механизмов внутри-и межполового отбора. Нет весомых оснований вообще увязывать эволюцию ВПП у хомячков с действием механизмов полового отбора. Вместе с тем поставленный нами эксперимент отчет-ливо демонстрирует трудности проверок теоретических моделей выбора партнера, таких как "Гипотеза гандикапа" Захави или ее популярная конкретизированная форма, известная под именем "Гипотезы иммунного гандикапа" Фольстадта и Картера. Эти трудности обсуждают-ся в статье. Поступила в редакцию 31.10.2016 г. Институт проблем экологии и эволюции им. А. Н. Северцова РАН
... Musth is a physiological and behavioural condition exclusive to male elephants, which is manifested by bouts of elevated testosterone, aggression and heightened sexual activity (Hollister-Smith et al. 2007). Musth is an important aspect of male elephant society as musth in older, dominant males suppresses musth in younger males, maintaining discipline in elephant society (Archie et al. 2006;Hollister-Smith et al. 2007;Poole 1989;Wittemeyer & Getz 2007). In turn, dominance hierarchies in elephants are strongly linear to ensure that only the oldest, most dominant males with the best genes gain access to receptive females, maintaining the fitness of the population as a whole (Clutton-Brock 1988). ...
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Elephant populations in South Africa are largely confined to fenced reserves and therefore require continued management to prevent high elephant densities that may cause habitat degradation. Growing human populations surrounding these reserves limit the possibility for wildlife range expansion, adding socio-economic considerations to the growing list of challenges reserve managers must contend with. Often, reserves have therefore opted to manage elephant population growth using various contraceptive methods to reduce birth rates, with lethal control acting as a last resort. Reserve owners at the Pongola Game Reserve South in northern KwaZulu-Natal opted to vasectomise the oldest male elephants to limit elephant population growth. Besides the reduction in birth rates, vasectomies were anticipated to have minimal impacts on behaviour. This study aimed to examine behavioural implications of treatment by monitoring musth, dominance and social behaviours of vasectomised males. Physical and behavioural observations of vasectomised males were recorded using instantaneous scan sampling and continuous focal samples of study individuals between 2011 and 2016. These data were also collected for non-treated adolescent males, with which to substantiate potential impacts of vasectomies. This case study has revealed that the behaviour of the vasectomised males was not influenced by vasectomies: musth was displayed as anticipated in the oldest males; a linear dominance hierarchy was maintained, headed by the oldest individual, and association patterns with female groups remained intact. Further, the younger non-treated males fell in line with the overall dominance hierarchy. This unique post-treatment study supports the use of vasectomies as a relatively cost-effective (one-off treatment), low-risk and successful tool for the management of elephant population growth, and an option which is preferable to both lethal control and hormonal contraceptives. Further research to establish the impacts of vasectomies on female behaviour and population dynamics is recommended.
... The observed blue whale behavior, in all three cases, likely represented a competitive behavior linked to reproduction, as described by Sears and Perrin (2002). Escorting behavior (a male accompanying a female) is known to occur in many animal taxa, e.g., humpback whales (Megaptera novaeangliae) and African elephants (Loxodonta africana), as well as in various bird and primate species; Alberts, Altmann, & Wilson, 1996;Baker & Herman, 1984;Birkhead, 1979;Birkhead, Johnson, & Nettleship 1985;Clapham, Palsbøll, Mattila, & Vasquez, 1992;Poole, 1989;Tyack & Whitehead, 1982). Escorting allows a male to defend a female, limiting access of other males to the female and thereby increasing the likelihood of siring potential offspring. ...
... Our framework can therefore investigate species that show intraspecific variation in their social systems (Schradin, Hayes, Pillay, & Bertelsmeier, 2018). Examples include those where males and females live separately outside of the breeding season, as in elephants and many ungulate species (Coulson, Albon, Guinness, Pemberton, & Clutton-Brock, 1997;Poole, 1989), or where sexes are organized in different ways, as in lions where one or multiple males' territory might encompass several cohesive female prides F I G U R E 1 Scheme of framework. The eight dimensions can be broadly classed into three categories (organizational, composition, and temporal). ...
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Mammalian societies represent many different types of social systems. While some aspects of social systems have been extensively studied, there is little consensus on how to conceptualize social organization across species. Here, we present a framework describing eight dimensions of social organization to capture its diversity across mammalian societies. The framework uses simple information that is clearly separated from the three other aspects of social systems: social structure, care system, and mating system. By applying our framework across 208 species of all mammalian taxa, we find a rich multidimensional landscape of social organization. Correlation analysis reveals that the dimensions have relatively high independence, suggesting that social systems are able to evolve different aspects of social behavior without being tied to particular traits. Applying a clustering algorithm allows us to identify the relative importance of key dimensions on patterns of social organization. Finally, mapping mating system onto these clusters shows that social organization represents a distinct aspect of social systems. In the future, this framework will aid reporting on important aspects of natural history in species and facilitate comparative analyses, which ultimately will provide the ability to generate new insights into the primary drivers of social patterns and evolution of sociality. Social organization is an aspect of animal social systems that has not been conceptualized yet and is often reduced to group size. This framework describes eight central dimensions of social organization to capture its diversity across mammalian societies. By applying our framework across 208 species of all mammalian taxa, we find a rich multidimensional landscape of social organization.
... Swelling of the perineal skin in multiple species of primates around the fertile phase of the cycle is hypothesized to have evolved because it stimulates competition among males (Nunn 1999). Acoustic signals of fertility work in the same manner and have been documented in the estrus calls of a number of different mammalian species and groups, such as African elephants, Old World monkeys, and bovids (Gouzoules et al. 1998;Poole 1989;Pradhan et al. 2006;Yeon et al. 2006). Delivering a call during times of peak fertility advertises the female's sexual receptivity and encourages dominant males to supplant subordinate males and engage in mating and subsequent mate guarding. ...
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... Musth presumably evolved to facilitate inter-and intrasexual interactions (LaDue et al., 2022); once thought to be largely solitary upon reaching sexual maturity, male Asian elephants are now known to have complex social lives into adulthood (Chiyo et al., 2011;Srinivasaiah et al., 2019;Keerthipriya et al., 2021). From field studies, we know that the condition of musth changes inter-and intrasexual association patterns (Poole, 1989b;Keerthipriya et al., 2020). We also expected to observe more frequent aggressive behavior during our observations of musth, as has been described in other in-situ (Poole, 1987(Poole, , 1989aGanswindt et al., 2005b) and ex-situ (Jainudeen et al., 1972a;Lincoln and Ratnasooriya, 1996;Flora et al., 2003;Ganswindt et al., 2005a;LaDue et al., 2014;Duer et al., 2016) studies. ...
Article
Complementary studies of wild and zoo-housed animals offer insight into behavioral variation across a range of conditions including the context under which various behaviors evolved in natural settings. This information can be used to improve the sustainability of in-situ and ex-situ populations and enhance the well-being of individuals. Managed ex-situ populations are critical to the long-term existence of Asian elephants, yet relatively little is known about male reproductive behavior compared to females. Male elephants undergo a unique sexual state called “musth” that further complicates in-situ and ex-situ management strategies. The ability to manage musth males to enhance breeding success and overall wellness of elephants is dependent upon better understanding how intrinsic and extrinsic factors influence male behavioral variation around musth. Here, we observed 62 free-ranging male Asian elephants in Sri Lanka and compared their behavior to observations from 26 elephants managed in facilities around the US. We hypothesized that musth is associated with significant behavioral changes that can be used to define distinct stages in the progression of musth. During observations, we quantified environmental variables and recorded musth status of each focal elephant using visual indicators (temporal gland secretions and urine dribbling). We showed that musth’s behavioral correlates (including changes in locomotion, foraging, alertness, and chemosensory behavior) were remarkably similar in wild and zoo-housed elephants. We also found that behavioral variation around musth was also associated with intrinsic (e.g., musth stage, age) and extrinsic factors (e.g., space availability, temperature) in zoo-housed, but not wild, elephants, indicating that musth is potentially plastic in changing environments. As musth progressed, we noted distinct behavioral signatures that define four stages of sexual activity in male elephants: non-musth, early musth, full musth, and post-musth. Finally, although we did not observe significant changes in overall social behavior (including aggression) during musth, we found that elephants increased the frequency with which they displayed certain behaviors associated with communication (e.g., alertness, chemosensory behavior, ear-flapping) in both populations. Together, these results indicate the significant behavioral changes that occur during musth in wild and zoo-housed elephants, and that musth progresses in distinct behavioral stages that can be easily distinguished by visual indicators. Studies like these serve to provide wildlife managers with information about a species’ unique, evolved behavioral strategies and how these seemingly fixed behaviors may be influenced by intrinsic and extrinsic factors in predictable ways.
... Reproductive coordination can be achieved between ovulating females and unrelated males using vocalizations over short and long distances [68,99]. Female African savanna elephants in mid-estrus use loud, low frequency calls to attract multiple males to their location, who then may compete for breeding access [42,100]. Male African savanna elephants use similar 'musth rumbles,' which are low-frequency calls that advertise sexual state [42,101,102]. ...
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Elephants are well known for their socio-cognitive abilities and capacity for multi-modal sensory perception and communication. Their highly developed olfactory and acoustic senses provide them with a unique non-visual perspective of their physical and social worlds. The use of these complex sensory signals is important not only for communication between conspecifics, but also for decisions about foraging and navigation. These decisions have grown increasingly risky given the exponential increase in unpredictable anthropogenic change in elephants’ natural habitats. Risk taking often develops from the overlap of human and elephant habitat in Asian and African range countries, where elephants forage for food in human habitat and crop fields, leading to conflict over high-quality resources. To mitigate this conflict, a better understanding of the elephants’ sensory world and its impact on their decision-making process should be considered seriously in the development of long-term strategies for promoting coexistence between humans and elephants. In this review, we explore the elephants’ sensory systems for audition and olfaction, their multi-modal capacities for communication, and the anthropogenic changes that are affecting their behavior, as well as the need for greater consideration of elephant behavior in elephant conservation efforts.
... Male elephants foraged significantly less when they were with females compared to when they were alone or with other males ( Figure 5). Elephants usually form same-sex groups [29]; when adult male elephants are associated with females, it is usually only for short periods of time, and for reproductive purposes when females are close to or in oestrus [28,72]. As a result, mixed-sex groups with receptive females are accompanied by more males compared to groups with females which are not in oestrus [73]. ...
Article
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African savannah elephants (Loxodonta africana) are well-known as ecosystem engineers with the ability to modify vegetation structure. The present study aimed to examine how male elephant foraging behaviour is affected across (a) season (wet versus dry); (b) time of day (before or after noon); (c) presence or absence of other elephants; and (d) reproductive state (musth versus no musth). Six radio-collared adult elephant bulls were observed twice per week from June 2007–June 2008 in Kruger National Park (KNP), South Africa. Using generalized linear mixed effect modeling, results indicate that elephant bulls graze more during the wet season and browse more during the dry season. To potentially offset the costs associated with thermoregulation during the heat of the day, KNP elephants spent more time foraging during the morning, and more time resting during the afternoon. Male elephants also foraged significantly less when they were associated with females compared to when they were alone or with other males. This is likely due to male–female associations formed mainly for reproductive purposes, thus impeding on male foraging behaviours. In contrast, the condition of musth, defined by the presence of related physical signs, had no significant effect on foraging behaviour.
... In another Asian elephant population, 15-20-year-old non-musth males engaged in sneak matings and 20-30-year-old non-musth males engaged in consortships more than expected by chance (Chelliah and Sukumar, 2013). As there is evidence for females preferring old musth males over young non-musth males in both African savannah (Poole, 1989) and Asian elephants (Chelliah and Sukumar, 2013), it would be interesting to find out how much mating and reproductive success is acquired by young non-musth males in this population. In the Samburu population of African savannah elephants, young males spent most of their sexually active state out of musth. ...
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We present a detailed study of male associations in the Asian elephant, using 6 years of data on identified, non-musth males. Adult males spent greater proportions of their time solitarily than in mixed-sex or in all-male groups. Old (over 30 years) males were sighted more frequently with their age-peers and less frequently with young (15–30 years) males than expected at random in all-male groups. Young males were not sighted more frequently with old males than with young males, and did not disproportionately initiate associations with old males. These results suggest that male associations, in the absence of females, may allow for old non-musth males to test strengths against age-peers. Social learning from older individuals did not seem to be important in male associations, unlike that observed in the African savannah elephant. We also found a constraint on the sizes of all-male groups, similar to that seen in female groups in our study population, and all-male groups were rarer and smaller than those in African savannah elephant. Although male associations were weak, most males had a significant top associate, with whom their association was the strongest, in female absence. In mixed-sex groups, male associations occurred at random, suggesting that males were tracking female groups independently. Differences in male social organization from that of the related African savannah elephant that occupies a similar niche possibly arise from differences in ecology.
... Females of both species may exercise some mate choice and have been found to respond more positively to mating attempts by large/musth males 23, 120 . In the Amboseli African savannah elephant population, old/musth males showed more mate guarding and obtained a higher number of matings than young/nonmusth males 120 . Subsequent paternity analyses also showed that age and musth affected paternity success, with older males amongst those in musth usually being more successful in siring offspring 63 . ...
Article
We review studies of the social systems of the living elephants—the Asian elephant (Elephas maximus), African savannah elephant (Loxodonta africana), and African forest elephant (Loxodonta cyclotis). Social systems include social organisation, the way relationships are structured, and the mating system; we describe each of these in turn, drawing from long-term observational studies and studies based on indirect methods in more inaccessible populations. Male and female elephants exhibit different adult lifestyles: females live in fission–fusion societies, whereas males disperse from their natal groups and subsequently associate with other males and females only temporarily. Associations and dominance relationships among females and among males may be complex and structured by factors such as genetic relatedness and relative ages. Elephants are polygynous and males compete amongst themselves for access to females. The outcome of such competition may be shaped by musth (a rut-like phenomenon) and age. Molecular markers have been used to understand aspects of social structure and mating system in some populations; we point to these studies and discuss further avenues of research. We also comment on how anthropogenic activities affect social systems, and the relevance of studying social systems in the context of conservation.
... Hypothesis 1: Prevention of Infanticide -females shouldencourage calling only when there are infants present, and hence presumably, not in the breeding season.Hypothesis 2: Hale Quality -females should encourage calling during the breeding season, or when there is least opportunity for infanticide to occur.Unfortunately, there are no data available from the present study to test whether females are inciting male-male competition as a means of selecting new mating partners (Hypothesis 2), as reported for several mammals (elephants -Poole, 1989? elephant seals-Cox & LeBoeuf, 1977? ...
Thesis
In the past, studies of territoriality in primates have concentrated on the role of males in territorial defence. But sociobiological theory of female strategies, and in particular Wrangham's model of female-bonded primate groups, suggest that in many species females should be investing considerable amounts of energy in defence of their food resources against other groups of females. The aims of this thesis are to: 1. investigate the roles of male and female Cercopithecus diana in territorial defence, and 2. determine whether female behaviour is consistent with food resource defence and male behaviour with reproductive resource defence as predicted by Wrangham's model. Annual activity budgets, feeding, ranging and territorial calling behaviour of two groups of C. diana are presented, alongside information on plant production cycles and the spatial distribution of potential food resources. Diana monkeys were observed living in groups of about 20 animals, comprising 1-2 adult males, 6-10 adult females, and subadults, juveniles and infants. Infants were born during the dry season. Diana monkeys feed on fruits, flowers, leaves and arthropods. Diet varies across the seasons following plant production cycles. Ranging patterns are determined, at least in part, by the spatial distribution of particular flowers and fruits that are important components of the diet. Females initiate territorial calling bouts significantly more often than does the group male. Intergroup encounters occurred very infrequently, but when they did it was the females, subadults and juveniles that were observed fighting with other groups while the males gave loud calls and jumping displays to one another. The thesis looks at whether females are defending food resources against other females. Territorial calling is investigated with respect to location within territory, and spatial distribution of important food resources. Male calling behaviour and defence of reproductive females is also considered. The implications of Diana monkeys calling behaviour are discussed in relation to theories of primate territoriality and defence with particular reference to Wrangham's model of female-bonded groups.
... [Thought question: Do you believe the last line of the abstract?] Poole [1989] Mate guarding, reproductive success and female choice in African elephants. Animal Behavior 37:842-49. ...
... However, all of these address only the symptoms of HEC and not the systemic issues associated with this complex problem (Mumby and Plotnik 2018). Instead, others have suggested animal-based approaches that integrate information about how known individual differences among elephants, including health (Evans and Harris 2012;Lynsdale et al. 2017), reproduction (Freeman et al. 2009;Crawley et al. 2017), behaviour (Poole 1989;Poole and Moss 1989;Freeman et al. 2010;McComb et al. 2011), cognition (Bates et al. 2008;Foerder et al. 2011;Plotnik et al. 2011) and personality (Lee and Moss 2012;Yasui et al. 2013;Seltmann et al. 2019), affect the propensity of these animals to engage in HEC. ...
Article
ContextHuman–elephant conflict (HEC) is a major threat to Asian elephants as humans and elephants are forced to share common resources. In Sri Lanka, human-dominated landscapes adjacent to protected areas promote high rates of HEC, especially in the form of crop-foraging by elephants. Crop-foraging can be dangerous to both elephants and humans involved in the conflict. Gunfire is a common way for human communities to deter crop-foraging elephants, and gunshot wounds are commonly described in this elephant population on necropsy. AimsWe sought to quantify and describe unique scar patterns among Asian elephants in a protected area, Wasgamuwa National Park, attributed to HEC. Methods We identified 38 adult female and 64 adult male elephants and recorded the age class and body condition of each with established standards. Using photographs, we counted the number, position, and relative size of all scars on each animal. Key resultsMale elephants had significantly more scars than did females, and for males, the number of scars increased progressively with age. Additionally, male elephants with higher body conditions had more scars. Finally, males tended to have more scars towards the head, especially at older ages. Conclusions Differences in total scar counts between the sexes in this population imply that male elephants in this area more frequently engage in HEC than do females, following observations previously described in the literature. Furthermore, the fact that male elephants acquired progressively more scars as they aged, and that fatter elephants had more scars, indicates that previous exposure to HEC may not have been a deterrent for future events among these males, and potentially, crops served as valuable food sources for these animals. Finally, the changing body locations of these scars with age in males possibly shows plastic behavioural responses during crop-foraging or lower tolerance by farmers towards habitual crop foragers. ImplicationsThese results emphasise the need for animal-based approaches to HEC mitigation. Similarly, conservation managers in Sri Lanka and other elephant range countries should investigate similar methods that estimate patterns of HEC to develop effective management strategies directly targeting animals most likely to engage in conflict.
... Bulls in musth will begin seeking females in estrous, while secreting chemical signals through urinary dribbling and temporal gland secretions (Ganswindt et al. 2005). However, Poole (1989b) observed males not in musth were capable of seeking a mate and successfully breeding, ...
Thesis
African elephants (Loxodonta africana) are becoming increasingly endangered due to illegal poaching and ivory trade markets. Preservation of the species is imperative to maintain fully functioning ecosystems, for future studies of social behaviour, and to allow future generations to revel in their magnificence. Conservation/game reserves, sanctuaries and zoos are attempting to make suitable captive environments that would aid successful reproduction while re-establishing wild African elephant populations. Unfortunately, there has been very little success with breeding in captivity. The objective of this review is to evaluate sexual behaviours in wild and captive populations to distinguish what features and reproductive techniques should be implements in captive environments to potentially achieve an effective and successful breeding program. The results of this review are that captive environments are limiting in many factors that impede natural behaviours that may lead to copulation and successful reproduction: group sizes and composition, age and sex of groups, and endocrinological changes due to stress. Natural environments are difficult to mimic which has led to development of reproductive technologies which may improve reproductive success. There have been some advancements in spermatozoa extension and preparation for cryopreservation and use in artificial insemination. Extenders with increased cholesterol from egg yolk have proven beneficial in maintaining sperm viability through transport and storage providing a promising outlook into the future of population restoration projects in captive environments. ii ACKNOWLEDGEMENTS
... Studies of birds (Wetton et al. 1995;Mountjoy and Lemon 1996;Sundberg and Dixon 1996;Wagner et al. 1996;Richardson and Burke 1999;O'Loghlen and Rothstein 2003), lizards (Lopez et al. 2003), insects (Somashekar and Krishna 2011), mammals (Poole 1989;Ferkin 1999;Komers et al. 1999), and fish (Côté and Hunte 1993) have shown a female preference for older males, as evidenced by higher reproductive success of older males (reviewed in the work of Brooks and Kemp 2001), and this relatively high reproductive success has occasionally been associated with relatively more intense advertisement signals (Mountjoy and Lemon 1996;Sundberg and Dixon 1996;O'Loghlen and Rothstein 2003). Some studies have also demonstrated the ability of females to use assessment signals to distinguish between adult and subadult individuals (Lopez et al. 2003;O'Loghlen and Rothstein 2003), and a cross-sectional study of captive voles has shown that females prefer the scents of older individuals (Ferkin 1999). ...
Article
Age-related changes in assessment signals occur in a diverse array of animals, including humans. Age-related decline in vocal quality in humans is known to affect perceived attractiveness by potential mates and voters, but whether such changes have functional implications for nonhuman animals is poorly understood. Most studies of age-related change in animal signals focus on increases in signal quality that occur soon after the age of first breeding ("delayed maturation"), but a few have shown that signal quality declines in older individuals after a mid-life peak ("behavioral senescence"). Whether other individuals are able to detect this senescent decline of assessment signals has not previously been tested. Here we use playback experiments to show that wild male swamp sparrows (Melospiza georgiana) respond more aggressively to songs from 2-year-old males as compared with songs from the same males when they are 10 years old. Senescence in signals that, like birdsong, affect reproductive success through intrasexual competition or mate choice may be of evolutionary significance.
... These 'mating calls' are a sexually selected trait, primarily used by males to attract female mates (reviewed in Fedorka & Mousseau, 2001) and advertise the male mating success (e.g., mice - White et al., 1998). Females use copulation calls to incite mate guarding behaviour in the male mates (e.g., African elephants - Poole et al., 1988;Poole, 1989) and to prevent or end unwanted copulations by attracting another high-ranking male (e.g., fowls -Pizzari, 2001;Løvlie et al., 2014). ...
Article
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Copulation calls are mating-associated vocalizations that are common in primates, with females vocalizing after copulation in several Old World monkeys and apes. Baboon females typically produce copulation calls that correlate with fertile phase. Calls are, thus, regarded as an upshot of cycle physiology and sexually selected calls. Here, we describe three captive troops of olive baboons wherein, against expectation, females suppressed vocalizing during copulations. Vaginal cytology, together with sexual swelling observations, confirmed that females experienced full receptive cycles. Ovulation did not affect vocal probability during sex, while copulation calls were predicted by male ejaculation just as in other Old World primate species. Results cast doubt on the existence of physiological triggers for baboon copulation calls. Social factors may instead play a larger role. Alterations in social structure (as typically observed in the wild) may be implemented strategically as captive enrichment in order to reveal how females in highly social primates change sexual strategies and, therefore, the use of their copulation calls.
... During fasting and low food availability, protein turnover is reduced and concentrations of T3 are low (St Aubin et al., 1996;Oritz et al., 2010). Elephant bulls in musth reduce their food intake and lose body condition (Poole 1987(Poole , 1989, and musth has been linked to reduced thyroid hormone concentrations (Chave et al., 2019). As shown for the EIA validation for the research presented here, low body condition scores were associated with low concentrations of mT3 in elephant bulls. ...
Article
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Conservation biologists can use hormone measurements to assess animals' welfare, reproductive state, susceptibility to stressors, as well as energy expenditure. Quantifying hormone concentrations from faecal samples is particularly advantageous as samples can be collected without disturbing animals' behaviour. In order for an endocrine marker to be useful for wildlife managers, we need to understand how extrinsic and intrinsic factors affect hormone concentrations in free-ranging animal populations. Thyroid hormones are linked to basal metabolic rate and energy expenditure. Previous research demonstrated that triiodothyronine (T3) can be measured successfully in faecal matter of African elephants, Loxodonta africana. However, to our knowledge, research into factors affecting changes in elephant T3 levels has only been carried out in captive elephants so far. Thus, we present the first study of faecal T3 metabolite (mT3) concentrations of a large population of free-ranging African elephants. Over 15 months, we collected faecal samples from identified (n = 43 samples) and unidentified (n = 145 samples) individuals in Madikwe Game Reserve, South Africa. We investigated whether vegetative productivity [normalized difference vegetation index (NDVI)] in interaction with mean monthly temperature, age and sex affected mT3 concentrations. We found a significant negative interaction effect of NDVI and temperature. Increasing NDVI was related to higher concentrations of mT3, but increasing temperature was related to a decrease in mT3 concentrations in individually identified and unidentified elephants. In unidentified individuals, juvenile elephants had significantly higher mT3 concentrations compared to adult elephants. Faecal T3 can successfully be quantified in samples from free-ranging elephant populations and thus provides insight into energy expenditure in large herbivores.
... Musth is similar to rutting behaviour in ungulates and is associated with periodic increases of testosterone secretion. Most matings occur in this period (Poole, 1989). During musth, the animal becomes more restless, energetic, aggressive and generally irritable and oversensitive to sound and movements. ...
Article
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Successful management of a violent male Asian elephant (Elephas maximus) in musth was carried out using 700 mg Xylazine HCl to obtain desired standing anaesthesia. The legs of elephant were tied with chains and tethered by using special jute rope to prevent his movement until the musth period was over. In brief, better awareness of people on physiological behavoiur of elephants for detection of musth as well as to adopt appropriate management procedures is referred
... Due to the difficulty of acquiring samples from free ranging live cetaceans, stranded individuals are frequently used to gain new insights into biolog-ical and phylogenetic histories (Drouot et al., 2004;Ottewell et al., 2016;Sabatier et al., 2015;Squadrone et al., 2015). As the largest toothed cetacean, the sperm whale (Physeter macrocephalus) shows migration patterns and social behaviors similar to some large terrestrial mammals, like Asian elephants (Gero et al., 2015;Mccomb et al., 2001;Poole, 1989;Stoeger and Baotic, 2016). The females show a strong philopatry to warmer regions around the equator and separate into social groups consisting of one or more matrilines, communicating with specific acoustic codas (Engelhaupt et al., 2009;Lyrholm and Gyllensten, 1998;Richard et al., 1996;Schulz et al., 2008;Whitehead, 1993). ...
Article
The globally distributed sperm whale (Physeter macrocephalus) has a partly matrilineal social structure with predominant male dispersal. At the beginning of 2016, a total of 30 male sperm whales stranded in five different countries bordering the southern North Sea. It has been postulated that these individuals were on a migration route from the north to warmer temperate and tropical waters where females live in social groups. By including samples from four countries (n = 27), this event provided a unique chance to genetically investigate the maternal relatedness and the putative origin of these temporally and spatially co-occuring male sperm whales. To utilize existing genetic resources, we sequenced 422 bp of the mitochondrial control region, a molecular marker for which sperm whale data are readily available from the entire distribution range. Based on four single nucleotide polymorphisms (SNPs) within the mitochondrial control region, five matrilines could be distinguished within the stranded specimens, four of which matched published haplotypes previously described in the Atlantic. Among these male sperm whales, multiple matrilineal lineages co-occur. We analyzed the population differentiation and could show that the genetic diversity of these male sperm whales is comparable to the genetic diversity in sperm whales from the entire Atlantic Ocean. We confirm that within this stranding event, males do not comprise maternally related individuals and apparently include assemblages of individuals from different geographic regions.
Article
en • In non‐human mammals, sexual conflict should be particularly intense because males rarely provide parental care. An expected consequence of sexual conflict is male aggression towards mates. Considering how complex measurements and interpretations of behaviours such as sexual aggression and sexual coercion are, I preferred to define operationally, as ‘sexual disturbance’, any male behaviour towards females during the pericopulatory period that can be costly for females. • The objectives in this review were as follows: 1) to estimate how widespread sexual disturbance is among mammals, 2) to analyse the types of female response to sexual disturbance, and 3) to characterise the costs of sexual disturbance to females. I conducted a systematic review by searching the literature in the Web of Knowledge database using the search tools available for 19 main journals, and I conducted a qualitative review via a taxon‐by‐taxon analysis. • Sexual disturbance was frequent in four of the 32 mammalian orders: Primates, Artiodactyla, Carnivora, and Cetacea, which all include highly polygynous taxa. The most common expression of sexual conflict around copulation is seen in behaviours associated with female retention attempts that cause minor harm. Research suggests that the most common response of females to sexual disturbance comprises female grouping around a dominant male. RESUMEN EN ESPAÑOL es • En mamíferos no‐humanos, el conflicto sexual puede ser particularmente intenso debido a que los machos raramente proveen cuidado parental. Una consecuencia esperada del conflicto sexual es la agresión sexual hacia las parejas reproductivas. Considerando que las medidas e interpretaciones de conductas tales como la agresión sexual y la coerción social pueden ser muy complejas, preferí definir operacionalmente como 'perturbación sexual' a cualquier comportamiento de los machos hacia hembras durante el período peri‐copulatorio que podría ser costoso para las hembras. • Los objetivos de esta revisión fueron: 1) estimar cuan difundida está la perturbación sexual entre los mamíferos, 2) analizar los tipos de respuestas de las hembras a la perturbación sexual, y 3) caracterizar los costos de la perturbación sexual para las hembras. Realicé una revisión sistemática buscando publicaciones en internet, usando las herramientas de búsqueda disponibles en 19 revistas científicas relevantes, y conduje una revisión cualitativa a través de un análisis taxón por taxon. • La perturbación sexual fue frecuente en cuatro de 32 órdenes de mamíferos: Primates, Artiodactyla, Carnivora y Cetacea, los cuales en todos los casos incluyen taxones altamente poligínicos. La expresión más común del conflicto sexual alrededor de la cópula son conductas asociadas a intentos de retención de las hembras que producen un daño menor.
Article
Coercive mate guarding, where males use aggression to control female movements, is a form of sexual coercion which functions to constrain female mate choice. Non-human primates, for example, herd females to keep them away from competing males, but male bottlenose dolphins (Tursiops aduncus) also herd females to keep them close to their alliance partners. Indeed, pairs and trios of male dolphins work together to sequester single estrus females and defend them from competing alliances. Yet how males facilitate such coordination remains unknown. Here, we investigate the vocal behaviour of allied male bottlenose dolphins during the herding of individual females, examining how the production of whistles and 'pops' (a threat vocalisation) varied with behavioural state and inter-animal distances. Allied males produced both whistles and pops significantly more often and at higher rates during social interactions, though they differed in function. Whistle rates increased significantly when new individuals joined the consorting group, consistent with previous work showing that whistles are part of a greeting sequence for this species. Whistle matching also appeared to play a role in within-alliance coordination. Pop vocalisations increased significantly when the nearest male to the female changed, likely inducing the female to remain close as the males coordinate a guard switch. Building upon prior research examining female movements in response to pops, we show that males approach the female and current guard whilst popping, leading to a guard switch. Our results provide new insights into the use of vocal signals during cooperative mate guarding between allied male dolphins.
Chapter
Power in Close Relationships - edited by Christopher R. Agnew February 2019
Article
We propose a practical concept that distinguishes the particular kind of weaponry that has evolved to be used in combat between individuals of the same species and sex, which we term intrasexually selected weapons (ISWs). We present a treatise of ISWs in nature, aiming to understand their distinction and evolution from other secondary sex traits, including from ‘sexually selected weapons’, and from sexually dimorphic and monomorphic weaponry. We focus on the subset of secondary sex traits that are the result of same‐sex combat, defined here as ISWs, provide not previously reported evolutionary patterns, and offer hypotheses to answer questions such as: why have only some species evolved weapons to fight for the opposite sex or breeding resources? We examined traits that seem to have evolved as ISWs in the entire animal phylogeny, restricting the classification of ISW to traits that are only present or enlarged in adults of one of the sexes, and are used as weapons during intrasexual fights. Because of the absence of behavioural data and, in many cases, lack of sexually discriminated series from juveniles to adults, we exclude the fossil record from this review. We merge morphological, ontogenetic, and behavioural information, and for the first time thoroughly review the tree of life to identify separate evolution of ISWs. We found that ISWs are only found in bilateral animals, appearing independently in nematodes, various groups of arthropods, and vertebrates. Our review sets a reference point to explore other taxa that we identify with potential ISWs for which behavioural or morphological studies are warranted. We establish that most ISWs come in pairs, are located in or near the head, are endo‐ or exoskeletal modifications, are overdeveloped structures compared with those found in females, are modified feeding structures and/or locomotor appendages, are most common in terrestrial taxa, are frequently used to guard females, territories, or both, and are also used in signalling displays to deter rivals and/or attract females. We also found that most taxa lack ISWs, that females of only a few species possess better‐developed weapons than males, that the cases of independent evolution of ISWs are not evenly distributed across the phylogeny, and that animals possessing the most developed ISWs have non‐hunting habits (e.g. herbivores) or are faunivores that prey on very small prey relative to their body size (e.g. insectivores). Bringing together perspectives from studies on a variety of taxa, we conceptualize that there are five ways in which a sexually dimorphic trait, apart from the primary sex traits, can be fixed: sexual selection, fecundity selection, parental role division, differential niche occupation between the sexes, and interference competition. We discuss these trends and the factors involved in the evolution of intrasexually selected weaponry in nature.
Article
Vocal communication plays an important role in the mating behaviour of arboreal squirrels. Callosciurus is a genus of tree squirrels that includes 15 species distributed in Southeast Asia, and congeneric species often inhabit the same forest. As closely related species of Callosciurus have the potential to interbreed, species recognition from mating calls may be a fundamental reproductive barrier. We compared seven acoustic characteristics of male mating calls in six Callosciurus species and estimated whether the species differences were clear enough to function as a cue. Discriminant function analyses (DFA) classified 87.4% of mating calls to the correct species. All of the calls by C. notatus, C. nigrovittatus and C. caniceps, and 88% of the calls by C. prevostii, were assigned to the correct species, while the percentage of correct classifications was lower in C. finlaysonii (71%) and C. erythraeus (63%). We compared these results with the genetic relationships to determine whether interspecific acoustic differences are caused by adaptive selection (habitat selection and body size) or by a stochastic process (drift). The genetic relationships among the six species were coincident with the differences in mating calls, which supports the stochastic divergence. Species-specific mating calls may be a useful cue for species recognition in Callosciurus, and thus these calls could be an effective trait for phylogenetic analysis in Callosciurus.
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The introduction of elephants into new groups is necessary for breeding programmes. However, behavioural studies on the reactions of these animals at first encounters are missing. In the present study, female African elephants (Loxodonta africana) living in zoos were observed during unifications with unfamiliar elephants (introduction of two to one females and one to two females; n = 6) and reunifications with related elephants (two mother–daughter-pairs; n = 4) that were separated for 2 and 12 years, respectively. First encounters of the elephants were observed and recorded by scan sampling. The parameters measured were (a) signs of the characteristic Greeting Ceremony, (b) distance to the fence separating the elephants during first contact, and (c) time until trunks touched for the first time. The data were statistically analysed with SPSS. The results showed that related elephants performed a full Greeting Ceremony on reunifications. Unrelated elephants only expressed a minor greeting. During first encounters, related elephants predominantly showed affiliative behaviour (p = 0.001), whilst unrelated elephants expressed more agonistic behaviour (p = 0.001). The distance to the fence was significantly smaller for related elephants than for unrelated elephants (p = 0.038). first contact of trunks occurred on average after 3.00 s. in related elephants and 1026.25 s. in unrelated elephants. These findings indicate that related elephants recognise their kin after up to 12 years of separation, meet them with a full Greeting Ceremony during reunification, and seek contact to the related elephant, while unrelated elephants are hesitant during unifications with unfamiliar elephants and express more agonistic behaviour. The results testify that zoo elephants show the same species-specific social behaviour as their conspecifics in the wild. It also confirms the cognitive abilities of elephants and the significance of matrilines for breeding programmes.
Article
During human evolution the prevention of cuckoldry has been an adaptive problem for the human male, solved in many other species by intensely guarding females during fertile periods. Signs of estrus in human females are much subtler than in many other species meaning that there is less certainty of the exact timing of the fertile period. This necessitates extended mate guarding which potentially reduces male fitness due to the loss of extra-pair fertilization opportunities and other fitness-compromising costs, such as reduction in the time spent acquiring status and resources. Patriarchy is a system of implicit and explicit rules of conduct, of power structures, and of belief systems that support male control over women’s reproduction and has existed for thousands of years. We examine the manifestations of patriarchy as a unique form of mate guarding which is able to function even in the absence of males. We explore historical and contemporary patriarchal practices such as rape, foot-binding, honor-killing and female genital mutilation and argue that males use patriarchy to increase the costs associated with female extra-pair copulation to increase their certainty of paternity. At the same time patriarchy functions to enforce in-pair childbearing by discouraging contraception and abortion. We propose that this form of control of females evolved to avoid an evolutionary trade-off between the benefits of monogamy and those of promiscuity for human males and that there has been selection on females for those compliant with patriarchy, who tended to have more surviving offspring. We also discuss patriarchy in the context of niche construction and propose that patriarchy is a cultural niche which has functioned to maximize individual males’ fitness. When viewed from an evolutionary perspective, the persistence of patriarchy into the 21st century is unsurprising.
Article
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Coercive mate guarding, where males use aggression to control female movements, is a form of sexual coercion which functions to constrain female mate choice. Non-human primates, for example, herd females to keep them away from competing males, but male bottlenose dolphins (Tursiops aduncus) also herd females to keep them close to their alliance partners. Indeed, pairs and trios of male dolphins work together to sequester single estrus females and defend them from competing alliances. Yet how males facilitate such coordination remains unknown. Here, we investigate the vocal behaviour of allied male bottlenose dolphins during the herding of individual females, examining how the production of whistles and ‘pops’ (a threat vocalisation) varied with behavioural state and inter-animal distances. Allied males produced both whistles and pops significantly more often and at higher rates during social interactions, though they differed in function. Whistle rates increased significantly when new individuals joined the consorting group, consistent with previous work showing that whistles are part of a greeting sequence for this species. Whistle matching also appeared to play a role in within-alliance coordination. Pop vocalisations increased significantly when the nearest male to the female changed, likely inducing the female to remain close as the males coordinate a guard switch. Building upon prior research examining female movements in response to pops, we show that males approach the female and current guard whilst popping, leading to a guard switch. Our results provide new insights into the use of vocal signals during cooperative mate guarding between allied male dolphins.
Article
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Darwin's1 hypothesis that male secondary sexual ornaments evolve through female preferences is theoretically plausible2-7, but there is little experimental field evidence that such preferences exist8-10. I have studied female choice in relation to male tail length in the long-tailed widowbird, Euplectes progne, and report here that males in which the tail was experimentally elongated showed higher mating success than males having normal or reduced tails. The possibility that intrasexual competition among males maintains the long tail was not supported: males with shortened tails held their territories as long as did other males. These results suggest that the extreme tail length in male long-tailed widowbirds is maintained by female mating preferences.
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The suckling behaviour of 130 freeranging elephant calves aged between birth and 4.5 years old was examined in Amboseli National Park, Kenya. Analyses of frequencies of suckling and durations of suckling bouts showed that males attempted to suckle more often, were more successful at their attempts, and as a result were estimated to have a higher milk intake than did female calves. Mothers were equally tolerant of their sons' and daughters' demands to suckle at young ages, but were less tolerant of their older sons' demands. The growth rates of males based on hind footprint length were faster than those of females from birth onwards. During drought years with low food availability, male calf survivorship in the first year was lower than that of female calves. During wet years, there was little difference between sexes in survivorship. It appeared that during dry years mothers were unable to sustain milk production at a level that met the metabolic requirements of their sons, and as result male calves were more likely to die. Females with a surviving son tended to have a longer interbirth interval than did females with a surviving daughter. We suggest that greater early maternal investment in male calves occurs because, in the highly-competitive polygynous mating system of elephants, size in adult male elephants is an important factor in mating success.
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Male-male competition and reproductive success of northern elephant seals, Mirounga augustirostris, was studied for six consecutive breeding seasons at Año Nuevo Island, California. The conclusions were as follows: (i) Less than one third of the males in residence copulate during a breeding season. A few males are responsible for the majority of copulations, (ii) The number and age of males copulating varies with: (a) harem location and topography, (b) the number of estrous females in the harem, and (c) the number of males competing for females, (iii) Copulation frequency is related directly to success in male-male competition, i.e., social rank. (iv) The same individuals may dominate breeding for three consecutive breeding seasons. (v) Successful males die within a year or two after their reproductive peak. (vi) The reproductive success of most males is nil or low because many die before reaching breeding age and some of those that reach maturity are prevented from mating by the highest ranking males. (vii) Individual strategies have important consequences for reproductive success, (viii) Male-male competition is a major cause of pup mortality prior to weaning. The potential reproductive success of males is much greater than that of females. Changes in colony number and composition affect the reproductive success of males as well as females.
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The phenomenon of musth in male Asian elephants, Elephas maximus, has long been recognized1. Musth, which has been likened to rutting behaviour in ungulates2, refers to a set of physical and behavioural characteristics displayed periodically by adult male elephants. The most obvious manifestations are a sharp rise in aggressive behaviour, copious secretions from and enlargement of the temporal glands, and the continuous discharge of urine3. It has been speculated that a similar phenomenon occurs in males of the African genus, Loxodonta africana, but most workers have concluded that it does not exist4-7. Here we show that musth does occur in the African elephant and that its manifestations are similar to those in the Asian elephant.
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Bulls in musth leave their home range, travel far and fast, initiate more contacts with distant breeding herds, show aggression which overrides normal social male hierarchies, probably mate more frequently than non-musth bulls and then return to their home range. This behaviour is associated with elevated levels of serum testosterone and dihydrotestosterone. Elephants normally show a high degree of fidelity to sexually segregated adjoining home ranges, which results in regular contact between the same bulls and cows. This breeding strategy is applicable to older, dominant bulls within the locally resident hierarchy. The musth adaptation is a second strategy, whereby younger, lower ranking bulls (25-35 yr) can ensure more contacts with cows and maximize their chances of breeding. Because musth bulls mate far from their normal ranges the strategy promotes gene flow and ensures outbreeding. -from Author
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Loxodonta africana were studied in National Park, Kenya. Five categories of oestrous behaviour are described: wariness, the oestrous walk, the chase, mounting, and consort behaviour. On average Amboseli females conceived once every 5 yr; for each of these conceptions the female may only have been in oestrus (lasting 2-6 days) once. Some females may exercise choice in mating partners. Possible short-term advantages to females exercising choice in mating partners are avoidance of harassment from other bulls; and large males in musth may be more likely to impregnate a female. A possible long-term advantage to mating with a large (older) male could be his ability to pass on a trait for longevity. Although females may be exercising choice among the size/age classes, male-male competition among the large males may override female choice on the individual level.-from Author
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The reproductive behaviour of a population of individually marked toads Bufo bufo was studied at a pond where males outnumbered females by between four and five to one. There was intense competition between the males for mates and only 20·5 % of them bred successfully. Of the successful males, 38·5 % got mates by fighting and displacing other males from the backs of females (takeovers). Larger males enjoyed greater reproductive success because they were stronger and better able to achieve takeovers. When competing for females, some males searched at the spawn site while others searched away from spawn. The numbers searching in the two areas can be predicted by a model which assumes that unpaired males distribute themselves so that there is a spatial ESS, where individuals have equal expectations of finding a female both at and away from the spawning ground.
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Females that mate with the most fit male available leave more viable offspring than females that mate with males of lesser fitness. We describe a mechanism by which females facilitate mating with a superior genotype, as reflected by age, social rank, and sexual experience, without exerting choice. Female elephant seals increase the probability of mating with a mature, high-ranking male by simply rejecting all copulatory attempts during early estrus. Females protest loudly when mounted; this signals all nearby males and activates the dominance hierarchy. The probability that the mounting male will be interrupted by another male is a function of the mounter's social rank. The lower his rank, the higher the probability of interruption. The result is that mature males of high social rank have more time and freedom to attempt copulation, and they succeed in doing most of the mating. The behavior of the female intensifies this monopoly by making it more difficult for young, subordinate males to copulate. A similar female strategy seems to operate in several species where the female is courted by several males. Influencing the genotype of her offspring is an important means by which a female can increase her inclusive fitness. This aspect of sexual selection has been neglected.
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Male Loxodonta africana spent more time in association with females during musth than during non-musth periods. Males were more aggressive during their musth periods. Occurrence and duration of musth were age-related: no male under 24 yr was seen in musth; bouts of musth among younger individuals were short and sporadic, while older males experienced longer more predictable periods of musth on an annual basis. Males in musth were observed year-round, but frequency of musth males was highest during and following the 2 rainy seasons and, in general, good rainfall years had higher frequencies of males in musth than did poor rainfall years. Number of males in musth per month correlated closely with the number of females observed in estrus, but since estrus lasts only 4-6 days, while musth may last several months, onset of musth was not necessarily triggered by onset of estrus in a particular female. The musth periods of different males were asynchronous and each male came into musth at a specific time of year. This period was relatively consistent from one year to the next, particularly among older males. Males in musth advertised their heightened sexual and aggressive state through visual and olfactory signals and by vocalizing. These signals announce identity, condition and location to both rival males and to potentially receptive females. The physical and behavioral characteristics and temporal patterning of musth are very similar in African and Asian elephants. -from Author
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Seven major types of sampling for observational studies of social behavior have been found in the literature. These methods differ considerably in their suitability for providing unbiased data of various kinds. Below is a summary of the major recommended uses of each technique: In this paper, I have tried to point out the major strengths and weaknesses of each sampling method. Some methods are intrinsically biased with respect to many variables, others to fewer. In choosing a sampling method the main question is whether the procedure results in a biased sample of the variables under study. A method can produce a biased sample directly, as a result of intrinsic bias with respect to a study variable, or secondarily due to some degree of dependence (correlation) between the study variable and a directly-biased variable. In order to choose a sampling technique, the observer needs to consider carefully the characteristics of behavior and social interactions that are relevant to the study population and the research questions at hand. In most studies one will not have adequate empirical knowledge of the dependencies between relevant variables. Under the circumstances, the observer should avoid intrinsic biases to whatever extent possible, in particular those that direcly affect the variables under study. Finally, it will often be possible to use more than one sampling method in a study. Such samples can be taken successively or, under favorable conditions, even concurrently. For example, we have found it possible to take Instantaneous Samples of the identities and distances of nearest neighbors of a focal individual at five or ten minute intervals during Focal-Animal (behavior) Samples on that individual. Often during Focal-Animal Sampling one can also record All Occurrences of Some Behaviors, for the whole social group, for categories of conspicuous behavior, such as predation, intergroup contact, drinking, and so on. The extent to which concurrent multiple sampling is feasible will depend very much on the behavior categories and rate of occurrence, the observational conditions, etc. Where feasible, such multiple sampling can greatly aid in the efficient use of research time.
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Calls at frequencies below the range of human hearing were recorded from two groups of captive Asian elephants (Elephas maximus). Most of the calls ranged in frequency from 14 to 24 Hz, with durations of 10–15 s (Fig. 1). With the nearest elephant 5 m from the microphone, sound pressure levels were 85 to 90 dB (re 20 Pa). These calls occurred in a variety of circumstances. Elephants are the first terrestrial mammals reported to produce infrasound. These calls may be important in the coordination of behavior in thick vegetation or among separated groups of elephants.
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The calls of male field crickets attract sexually receptive females. In Gryllus integer, males differ from one another in their durations of uninterrupted calling (calling bout lengths). Tape recordings of the calls of 50 wild-caught males revealed that 14 males spent most of their calling time in short bouts (Fig. 1A), 18 in both short and long bouts (Fig. 1B), and 18 in long bouts (Fig. 1C). Re-recordings of 32 males after 3 weeks showed that calling bout lengths of individual males are stable with time (age) (Fig. 2). Three phonotaxis experiments investigated whether calling bout lengths of males affect female preferences. They demonstrated that (1) females can discriminate among conspecific males on the basis of calls alone; (2) females are preferentially attracted to males with long calling bout lengths; and (3) calling bout length is the specific factor responsible for preferential attraction. These results precisely identify a criterion that females use to discriminate among potential mates of their own species.
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Experiments were designed to determine the effects of male pigmentation patterns on female choice in guppies. When presented with a series of variably-colored males, females of different genetic strain consistently exhibited similar preferences (Tables 1 and 2), preferring those males with the greatest development of both carotenoid and iridescent pigments (Table 3). A partial rank correlation analysis of pigments of males indicates positive correlations between the iridescent and carotenoid pigments and also between melanins and showiness (Table 4). Only when either the carotenoid or iridescent pigments were held constant was there any effect of the other pigments on the ranking order of males by the females. Other pigments appear to be relatively unimportant in influencing female choice of males. These results indicate that females discriminate among males on the basis of color and that females of different strains prefer the same male colors rather than those characteristics of males of their own strain. The results support those models of sexual selection that hold that sexually selected traits honestly advertise the phenotypic and genetic qualities of males; they do not support models of runaway selection for particular male traits, such as first proposed by Fisher (1930).
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Several types of low frequency calls made by African elephants, Loxodonta africana, and the contexts in which they occurred are described. These calls had fundamental frequencies ranging from 14–35 Hz and sound pressure levels as high as 1033dB (re 20 Pa) at 5 m from the source. Very low frequency sounds are subject to very little environmental attenuation, suggesting that sounds at the frequencies and sound pressure levels measured from elephants may be audible to conspecifics several km away. Long-term records on the behavior of elephants and on the contexts of specific call types suggest that elephants make use of infrasound in the spatial coordination of groups and as they search for mates.
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The evolution of female choice is controversial. The males of many polygynous species have bizarre features such as long and elaborate tails which seem to be maladaptive. If females choose to mate with such males how could choice genes increase in frequency? It is argued that (a) male age may be an indicator of fitness with older males having a higher average fitness than young males, (b) the size and complexity of many male ornaments and weapons are positively correlated with age. Females that choose males with, say, a longer than average tail are choosing males who are older than average. The choosy females therefore have male and female offspring with a higher fitness than the progeny of randomly mating females. As female choice genes spread the size or complexity of the age-dependent ornament increases. Mutations increasing size or complexity of such ornaments will also spread. A stable situation will be reached when the advantage of choosing older males is balanced by the disadvantage of, say, very long tails.
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Predictions derived from game theory suggest that animals should not signal their intentions during conflict situations. However, during the period of musth, male elephants,Loxodonta africana, announce a state of heightened aggression with signals that are unbluffable. Since smaller musth males in poor condition are able to dominate larger, normally higher-ranking, non-musth males in good condition, musth provides a useful system with which to examine the possibility of honest signalling of motivation, rather than of fighting ability. Despite the highly aggressive state of males in musth, escalated contests are extremely rare. The behaviour of musth and non-musth males suggests that opponents are able to estimate their often rapidly changing roles in the asymmetries with relative accuracy. Since, unlike most other rutting mammals, elephants have asynchronous sexually active periods, resource value varies both with age and the fluctuating sexual state of a particular individual. It is suggested that musth may be a case where information about resource value is conveyed.
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For red deer stags, fighting both has appreciable costs and yields considerable benefits. Up to 6% of rutting stags are permanently injured each year, while fighting success and reproductive success are closely related, within age groups as well as across them. Fighting behaviour is sensitive to changes in the potential benefits of fighting: stags fight most frequently and most intensely where potential benefits are high and tend to avoid fighting with individuals they are unlikely to beat. The relevance of these findings to theoretical models of fighting behaviour is discussed.
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BECAUSE the primates are a particularly well studied group they provide a rare opportunity to investigate the adaptive significance of species differences in sexual dimorphism in body size. We describe here an investigation of the relationship between the degree of sexual dimorphism and three variables which are predicted might affect it.
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Combination of seven surveys of blood parasites in North American passerines reveals weak, highly significant association over species between incidence of chronic blood infections (five genera of protozoa and one nematode) and striking display (three characters: male "brightness," female "brightness," and male song). This result conforms to a model of sexual selection in which (i) coadaptational cycles of host and parasites generate consistently positive offspring-on-parent regression of fitness, and (ii) animals choose mates for genetic disease resistance by scrutiny of characters whose full expression is dependent on health and vigor.
Observational study of behavior: sampling methods
  • Atlmann
On the ecology and behaviour of the African elephant
  • Douglas-Hamilton
Musth and male-male competition in the African elephant
  • Poole