Male Elephant Research Articles

High-density lipoprotein remains elevated despite reductions in total cholesterol in fasting adult male elephant seals (Mirounga angustirostris)

We examined changes in lipid profiles of 40 adult northern elephant seal bulls over the 3-month breeding fast and the 1-month molting fast to investigate impacts of fasting on serum total cholesterol (TC), triglycerides (TG) and lipoproteins. Total cholesterol and low-density lipoprotein (LDL) levels were initially high (3930 ± 190mgL(-1)and 1610 ± 170mgL(-1), respectively) and decreased significantly over the breeding season. Total cholesterol and LDL declined significantly with adipose tissue reserves (p<0.001), and LDL levels as low as 43 mgL(-1) were measured in seals late in the breeding fast. Less dramatic but similar changes in lipid metabolism were observed across the molting fast. High-density lipoproteins (HDL) remained consistently elevated (>1750 mgL(-1)) suggesting that elephant seals defend HDL concentrations, despite significant depletion of TC and LDL across the breeding fast. Triglyceride levels were significantly higher during the molt, consistent with lower rates of lipid oxidation needed to meet metabolic energy demands during this period. The maintenance of HDL during breeding is consistent with its role in delivering cholesterol from adipose tissue for steroidogenesis and spermatogenesis and potentially mitigates oxidative stress associated with fasting.

Directionality of male northern elephant seal (Mirounga angustirostris) threat calls and how it influences receiver behavior.

Many animal sounds are directional in which the sound energy is focused in a direction that depends on the signaler’s orientation. In the 1970s, Ron Schusterman quantitatively showed this in barking California sea lions and dogs. Several investigators have suggested ways that such features might be particularly useful among individuals in acoustic communication networks. However, only a few have tested such hypotheses experimentally and even fewer have investigated how directional signals affect receiver behavior. In this study, we measured directivity patterns of male northern elephant seal threat calls and used an acoustic playback approach to determine how call directionality influenced the responses of male seals in reproductive competition. We collected data on adult and older subadult seals on a breeding rookery (Ano Nuevo State Park) over three field seasons. Threat calls had substantial directionality, particularly at frequencies above 1 kHz and responses to playbacks depended on call directivity patterns. Males moved farther away from the playback source when it simulated a caller oriented toward them compared to when playbacks simulated a caller oriented away from them. These results suggest that threat call directionality provides meaningful information about the auditory scene and spatial orientation of male elephant seals in reproductive competition.

Vocalization source levels of adult male northern elephant seals (Mirounga angustirostris).

Aerial vocalization source levels were obtained for adult male northern elephant seals from 1999–2010. Vocalizations from known individuals (marked within years) were selected from three breeding seasons (1999–2000, 2004–2005, and 2009–2010) evenly spaced during this interval so that it is unlikely animals were resampled across seasons. Sound pressure levels of calls were measured on‐axis (0‐deg orientation) at 1‐m range using Brel and KJær 2203 and 2250 precision sound level meters. Calls almost always occurred in series, as previously described; the maximum received level for any pulse in each series is used as the source level. Source levels are reported for individuals with at least four complete bouts. All sex/age classes were measured; the adult male data will be discussed and compared with other mammals in terms of rms levels (two temporal weighting functions) and peak sound pressure levels. Results indicate that calls almost always exceed 100 dB rms (re: 20 μPa) with peak levels regularly exceeding 120 dB. These loud sounds might suggest long‐range communication, but considering hearing data Ron Schusterman and Dave Kastak first collected on this species and environmental noise levels in their rookeries, intense signals are likely required even for the small ranges over which they apparently function. [Funding provided by ONR.]

Vocal recognition of individuals versus relative dominance rank among breeding male northern elephant seals (Mirounga angustirostris).

Whether an animal truly recognizes an individual or a simple rule-based category (e.g. neighbor or offspring) has important behavioral and evolutionary implications such as the accuracy of social reciprocity. Many tests of individual recognition have focused on neighboring territorial males (dear enemy or neighbour-stranger recognition). Unfortunately the static territorial context of these tests, mostly with male songbirds, opens them to the criticism of being merely associative habituation. More dynamic mating assemblages, such as leks where vocally advertising animals encounter numerous others, are a potentially rich and largely untested alternative. The female defense polygyny practiced by male northern elephant seals during terrestrial breeding is such a dynamic system. To examine whether elephant seals were recognizing individuals or dominance categories we conducted a total of 53 playback experiments to 18 males at Ano Nuevo State Reserve. Each playback was a series of threat calls assigned to four dominance conditions relative to the subject. Dominance was based on the outcomes of interactions among contesting male dyads. Responses were measured using three assays in situ and from video records of each experiment. Results indicate that males do recognize familiar individuals although responses are primarily based on relative dominance rank.

Movement Patterns of African Elephants (Loxodonta africana) in Different Habitat Types

In this paper we analyse the daytime movements of African elephants (Loxodonta africana) in different habitats in the Pongola Game Reserve, South Africa. On average adult males moved faster than females in all habitat types except when grouped together (then females moved at the faster male pace). Elephants demonstrated distinct movement patterns in different habitat types. All the movement parameters indicate that the elephants turned less the further they were from a large permanent body of water (Jozini Dam) and for males with increasing distance to the females. Male and female elephants turned more in habitat types that had favourable resources such as forage and shade, than they did in unfavourable habitats. Thus, the elephants used a direct movement strategy — turning less — when needing to get to a destination more quickly (e.g. toward water or mates), rather than significantly increasing their speed. It is hypothesized that these elephants are optimizing energy efficiency while still varying their...

Association patterns of African elephants in all-male groups: the role of age and genetic relatedness

Strong social bonds are uncommon among male mammals. In many mammals, however, males form all-male groups, providing opportunities for male–male bonds to emerge. We examined association patterns of male African elephants, Loxodonta africana, in all-male groups and assessed the influence of age and genetic relatedness on these associations. We also examined the influence of age and genetic relatedness on the choice of sparring partners in male elephants. Males had many weak and random associations and few valuable relationships. Male associations were positively correlated with genetic relatedness, suggesting that kinship influences patterns of male associations. Male associations were negatively correlated with age disparity, and males were more likely to spar with other males closer in age to themselves. These results suggest that males associate with other males of similar age in part because sparring may facilitate the development and maintenance of motor and psychological responses to sudden and unexpected events that occur during play; this may help prepare males for male–male competition. We also found that older males had high centrality and strength in social networks, suggesting that older males influence the cohesion of male social groups. Consequently, the elimination of older males from elephant populations by poachers or trophy hunters could negatively affect social cohesion in male elephant groups. Finally, we found that age and genetic relatedness were not significantly correlated, suggesting that male associations based on age and relatedness did not overlap. These findings highlight the complexity of male social relationships in all-male groups.

No risk, no gain: effects of crop raiding and genetic diversity on body size in male elephants

Body size is an important influence on the life history of males of polygynous mammals because it is usually highly correlated with fitness and is under intense selection. In this paper, we investigated the effect of high-risk foraging behavior (crop raiding) and genetic heterozygosity on male body size in a well-studied population of African elephants. Crop raiding, the foraging on cultivated food crops by wildlife is one of the main causes of wildlife human conflict and is a major conservation issue for many polygynous mammals that live in proximity to agriculture or human habitation. Body size was estimated using hind foot size, a measure strongly correlated with stature and mass. Crop raiding predicted male size in adulthood, with raiders being larger than nonraiders. However, elephants that became raiders were neither larger nor smaller for age when young. Enhanced growth rates and size among raiders suggest that taking risks pays off for males. Lastly, genetic heterozygosity had no effect on size for age in male elephants, most likely because low-heterozygosity males were rare. Risky foraging behavior can evolve as a result of strong sexual selection for large size and condition-dependent mating success in males. We discuss the implications of these results for managing human‐wildlife

EFFECTS OF RAINFALL, HOST DEMOGRAPHY, AND MUSTH ON STRONGYLE FECAL EGG COUNTS IN AFRICAN ELEPHANTS (LOXODONTA AFRICANA) IN NAMIBIA

Wild African elephants (Loxodonta africana) are commonly infected with intestinal strongyle parasites. Our objective was to determine baseline fecal strongyle egg counts for elephants in the northeast region of Etosha National Park, Namibia and determine if these numbers were affected by annual rainfall, elephant demography (age of individuals and composition of groups), and hormonal state of males. We found that matriarchal family group members have significantly higher fecal egg counts than male elephants (bulls). Among family group members, strongyle egg counts increased with age, whereas among bulls, strongyle egg counts decreased with age. Years of higher rainfall were correlated with decreased numbers of strongyle eggs among bulls. Finally, bulls were not affected by their physiologic (hormonal) status (musth vs. nonmusth). These results suggest that infection by strongyle parasites in Namibian African elephants is a dynamic process affected by intrinsic and extrinsic factors including host demography and rainfall.

Elevated levels of stress hormones in crop-raiding male elephants

Crop raiding is one of the most common forms of human–elephant conflict. Deterring elephants from raiding crops requires an understanding of the factors influencing the behavior of the individuals involved. We collected fecal samples from five group ranches in southern Kenya where crop-raiding incidents had occurred (n=10) and two protected areas, Amboseli National Park (n=24) and Maasai Mara National Reserve (n=20). We used molecular sexing to sex the individuals and radioimmunoassay kits to determine the level of glucocorticoid metabolites (i.e. stress hormones) in their dung. All crop-raiding individuals were male and had a significantly elevated concentration of glucocorticoid metabolites as compared with the Amboseli elephants (W=12, P=0.0005). We detected no significant difference between Maasai Mara elephants and either Amboseli or the crop-raiding elephants when just males were compared. Our results suggest that crop raiding may be related to stress in elephants.

Environment and activity affect skin temperature in breeding adult male elephant seals (Mirounga angustirostris)

The large body size and high rates of metabolic heat production associated with male mating success in polygynous systems creates potential thermoregulatory challenges for species breeding in warm climates. This is especially true for marine predators carrying large blubber reserves intended for thermoregulation in cold water and fuel provision during extended fasts. Thermographic images were used to measure changes in skin temperature (T(S)) in adult male northern elephant seals (Mirounga angustirostris) over the breeding season. Environmental variables, primarily ambient temperature and solar radiation, were the principal determinants of mean and maximum T(S). When controlled for environmental variables, dominance rank significantly impacted mean T(S), being highest in alpha males. Behavioral activity significantly influenced T(S) but in a counter-intuitive way, with inactive males exhibiting the highest T(S). This was likely due to strong impacts of environmental variables on the kinds of behavior exhibited, with males being less active on warm, humid days at peak solar radiation. We classified thermal windows as areas in which T(S) was one standard deviation greater than mean T(S) for the individual seal within a thermograph. Thermal features suggest active physiological thermoregulation during and after combat and significant circulatory adaptations for heat dumping, as evidenced by recurring locations of thermal windows representing widely varying T(S) values. Frequent observations of localized T(S) above 37°C, particularly after combat, suggest the production of thermoregulatory stress during breeding behavior. Our findings demonstrate the importance of environmental drivers in shaping activity patterns during breeding and provide evidence for thermoregulatory costs of successful breeding in large polygynous males.

MALE ELEPHANT SEALS STAY STILL TO KEEP COOL

![Figure][1] The mating season is a time of great exertion for male elephant seals. Defending their harem, the males fast and lose approximately 36% of their body mass during their mating marathon. Not surprisingly, the well-insulated animals generate colossal amounts of heat during their

The spatial scaling of habitat selection by African elephants

1. Understanding and accurately predicting the spatial patterns of habitat use by organisms is important for ecological research, biodiversity conservation and ecosystem management. However, this understanding is complicated by the effects of spatial scale, because the scale of analysis affects the quantification of species-environment relationships. 2. We therefore assessed the influence of environmental context (i.e. the characteristics of the landscape surrounding a site), varied over a large range of scales (i.e. ambit radii around focal sites), on the analysis and prediction of habitat selection by African elephants in Kruger National Park, South Africa. 3. We focused on the spatial scaling of the elephants' response to their main resources, forage and water, and found that the quantification of habitat selection strongly depended on the scales at which environmental context was considered. Moreover, the inclusion of environmental context at characteristic scales (i.e. those at which habitat selectivity was maximized) increased the predictive capacity of habitat suitability models. 4. The elephants responded to their environment in a scale-dependent and perhaps hierarchical manner, with forage characteristics driving habitat selection at coarse spatial scales, and surface water at fine spatial scales. 5. Furthermore, the elephants exhibited sexual habitat segregation, mainly in relation to vegetation characteristics. Male elephants preferred areas with high tree cover and low herbaceous biomass, whereas this pattern was reversed for female elephants. 6. We show that the spatial distribution of elephants can be better understood and predicted when scale-dependent species-environment relationships are explicitly considered. This demonstrates the importance of considering the influence of spatial scale on the analysis of spatial patterning in ecological phenomena.

The ranging behaviour of a large sexually dimorphic herbivore in response to seasonal and annual environmental variation

AbstractThe allometric relationships of body size play a principle role in determining how large herbivores respond to the marked spatial and temporal heterogeneity of the savanna biome. Using location data collected over an 8‐year period from five distinct study sites, we investigated the influence of environmental variation (using phenological and rainfall data) on the ranging behaviour of the African elephant (Loxodonta africana), a species that exhibits pronounced sexual dimorphism. Both sexes expanded their annual ranges during years of high rainfall and contracted their ranges during periods of resource scarcity, concurring with the hypothesis that abiotic factors dictate the distribution of large generalist herbivores at the landscape scale. However, female elephant did not exhibit the same consistent response to rainfall at the seasonal scale. Furthermore, male elephant demonstrated a reduction in their daily displacement distances during the dry winter season, and altered their movement rates on the basis of seasonal rainfall. These results suggest that male elephant are able to consistently adapt their movement behaviour according to forage quality and abundance. Smaller‐bodied female elephant on the other hand, are unlikely to exhibit the same flexibility in their ranging behaviour because of their higher relative nutritional demands, lower tolerance to fibrous forage and the social and energetic constraints of group living with juveniles. Our study highlights the major role that body size and sociality plays in the decision making of sexually dimorphic herbivores. These differences can have important implications for effective conservation and management, particularly with regard to demographic (e.g. survival) and ecological (e.g. habitat use) factors.

A Surge-Like Increase in Luteinizing Hormone Preceding Musth in a Captive Bull African Elephant (Loxodonta africana)

This study was conducted to determine the correlation between reproductive hormones and musth in a male African elephant. Changes in circulating luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone and immunoreactive (ir-) inhibin and the degree of musth were evaluated for 4 years. LH increased 4 weeks before musth began. The highest concentrations of testosterone and ir-inhibin were observed from April to October. There were positive correlations among testosterone, ir-inhibin and musth behavior. These findings suggested that the surge-like LH in the pre-musth period might stimulate secretion of testosterone and ir-inhibin and thus initiate the musth behavior. This study also suggested that the high LH level before musth might be a useful biomarker for the beginning of the musth season.

Call directionality and its behavioural significance in male northern elephant seals, Mirounga angustirostris

Animals often produce sounds that are focused in a particular direction relative to the caller’s orientation. Although many studies have suggested ways in which directional signal design might have behavioural significance among vocally interacting individuals, there are few direct tests using experimental approaches. During the breeding season and while fasting on land, male northern elephant seals produce airborne threat calls during dyadic interactions when competing for mating opportunities. In this study, we investigated the directional cues of these calls and tested hypotheses regarding directional signalling with respect to the behaviour of receivers during vocally mediated male agonistic interactions. We then determined effects of vocal directionality on receiver responses using an acoustic playback approach. We found that male calls had substantial directionality, particularly at higher frequencies (>1000 Hz). Subordinate males responded more strongly by retreating when the caller faced the receiver compared to when the caller was at a right angle or faced away. We also found a significant difference in responses to playback sequences with different call directivity patterns. Males displayed significantly more negative phonotaxis (i.e. moved away) in response to playbacks that simulated a caller oriented towards them compared to when playbacks simulated a caller oriented away from them. These results suggest that the directionality of threat calls provides important information about the auditory scene and spatial orientation of conspecifics and that this trait, along with the receiver’s ability to extract this information, may have evolved as a consequence of its effect on the breeding success and fitness of the individual.

Visual Acuity and Heterogeneities of Retinal Ganglion Cell Densities and the Tapetum Lucidum of the African Elephant (Loxodonta africana)

The eyes of three adult male African elephants were examined, the retinas were whole-mounted, stained and analyzed to determine visual acuity. A range of small to large ganglion cell types were observed across the retinas. We observed three regions of high ganglion cell density, one in the upper temporal quadrant, a visual or horizontal streak and a smaller region at the nasal end of the horizontal streak. The peak density of ganglion cells observed was 5,280/mm², and our calculations indicate that the elephant has a maximal visual acuity of between 13.16 and 14.37 cycles/degree. We observed a heterogeneous structure of a tapetum lucidum, the cells of which were found to be most strongly aggregated behind the temporal and nasal densities of retinal ganglion cells. The strength of the tapetum lucidum was weaker posterior to the density of ganglion cells forming the horizontal streak. The morphology of the elephant eye appears to be such that it reflects: (1) the importance of trunk–eye co-ordination for feeding; (2) the importance of 24-hour vigilance for either predators or conspecifics, and (3) the arrhythmic nature of the daily activity of this animal, being useful both diurnally and nocturnally.

Long distance breeding dispersal of a southern elephant seal

Southern elephant seals range extensively during regular foraging excursions. Despite this they are highly philopatric and long range dispersal is rare. At Gough Island, southern Atlantic Ocean, we observed a breeding adult male elephant seal during September 2009, which had been tagged on its natal beach at Marion Island, southern Indian Ocean, in November 1998. The individual was resighted only once on Marion Island, 6 months after tagging. This 3,860 km movement represents dispersal (and likely gene flow) between distinct populations from different elephant seal geographical provinces. Given the polygynous breeding system of this species, the presence of this single male may have a disproportionate genetic effect on the small number of southern elephant seals breeding at Gough Island.

The Effect of Mating Motives on Risk Taking Likelihood Assessment in Men

According to sexual selection theory,intra-sex competition mainly among males leads to male characteristics known as weapons.The large body size and thick proboscis of male elephant seals and the robust horns and antlers of various ungulate stags are well-known examples of weapons.Inter-sex selection or mate choice,mostly exercised by the limiting sex or females,leads male characteristics known as ornaments.The vibrant colors of the guppy and the bright plumage of various birds are examples of ornaments.Whereas human males possess similar physical sex-dimorphic characteristics such as larger body frames (weapons),and lower voice pitch (ornaments),human sex-dimorphism is mainly shown as weapon-like (e.g.,aggression) and ornament-like behavior (e.g.,bragging).Human risk taking is such an ornament-like behavior because,like all ornaments which are functionally useless but are yet costly to sustain,risk taking behavior brings danger to its carriers without apparent functional purposes.Like ornaments,risk taking behavior is preferred by conspecific females who find its male carriers sexually attractive.The purpose of the present study was to test sexual selection theory on humans by investigating the association between risk-taking behavior and mating motives among men but not women.This hypothesis was tested against the rival hypothesis that risk taking may be externally motivated by monetary reward that renders similar effects on both men and women.These hypotheses were tested on a sample of 127 graduate students (62 males,mean age=21.47;SD= 1.59).In a between-group design,participants were exposed,on a computer screen,either to attractive opposite-sex pictures (the mating condition) or pictures of money or medals (the control or monetary reward condition).These two conditions were manipulated as a simple perceptual task where participants were instructed to decide on the location of each picture as it flashes on the screen (500 ms) by pressing one of two keys on the keyboard.This is to distract the participants from being aware of the intended experimental manipulation (mating versus monetary reward).To facilitate this distraction,attractive opposite sex pictures were also mixed with a small number of average-looking opposite sex pictures,and the monetary award pictures were mixed with a small number of non-reward scenes.After the picture exposure,each participant was given 19 different risk taking scenarios and was asked to assess the likelihood the participant would engage in each of the risk-taking behavior.The 19 risk-taking scenarios represent four domains of risk,including financial,health,social,and recreational risk.Composite scores representing the four domains were used as the dependent variables.Except for one of the four dependent variables,A 2 (mating vs.reward) × 2 (gender of the participants) ANOVA did not yield a significant interaction effect.However,separate t-tests were statistically significant,showing that men indicated higher likelihood to take risk after being exposed to attractive opposite-sex pictures than to reward pictures,whereas women did not show the difference in risk taking likelihood assessment besides social risk.Taking health risk for example,M=21.03 vs.18.67 under the mating vs.reward condition for men.The mean difference was statistically significant,p.01.For women,M=17.94 and 17.35,respectively.Other mean comparisons showed similar results which are reported in Table 1 in the main text.The results support sexual selection theory.Like most mammals,human males but not females have acquired ornament-like behaviors which are driven by mating motives.When attractive women are around,men are more likely to engage in functionally useless and potentially harmful behavior,which,however,are "useful" in the sense that they serve as signals of good genes.Thus,men's risk taking is driven by mating motives.Women are drawn to men's risk taking behavior for the same sexual selection reason,i.e.,women use the signals to select quality mates.In part to address reviewers' concerns,motives and need states serve as proximate cues that drive our behavior both consciously and unconsciously.In everyday life,mating motives,like many other motives,may remain unconscious most of the time which nonetheless drive and shape our behavior as is shown by the present study.

Endocrine correlates of musth and the impact of ecological and social factors in free-ranging African elephants ( Loxodonta africana)

Sexual activity in mature male African elephants is predominantly associated with the occurrence of musth, a state or condition which refers to a set of physical, physiological and behavioral characteristics, including an elevation in androgen levels. Although musth appears to be energetically costly, the degree to which it is associated with changes in adrenal endocrine function (e.g., glucocorticoid output) is still unclear. To investigate the possible effect of musth on adrenocortical function, and the impact of socioecological changes on androgen and glucocorticoid levels, six adult African elephant bulls were followed for 13 months in the Kruger National Park, South Africa, and observations and fecal sample collection for endocrine monitoring was carried out about twice weekly. Our data showed that the occurrence of musth was associated with reduced glucocorticoid output, suggesting that musth does not represent a physiological stress mediated by the hypothalamic–pituitary–adrenal axis. This confirms previous findings in captive-housed animals, providing evidence for a suppressive effect of the musth condition on adrenocortical activity. Furthermore, a seasonal effect on androgen and glucocorticoid levels was found, which appears to vary depending on the reproductive status of the animal. The results also indicate a relationship between the presence or absence of social partners and changes in testicular and adrenal endocrine activity. Finally, the data confirm previous findings in captive-housed elephants, that an elevation in androgen concentrations usually occurs before the onset of physical musth signs, and therefore support the idea that the change in androgen levels represents the initial stimulus for the musth condition.

Two records of male southern elephant seals (Mirounga leonina) on the Atlantic coast of Uruguay

Two records of male southern elephant seals (Mirounga leonina) on the Atlantic coast of Uruguay