Male Space Use Research Articles

Co‐occurrence of native white‐tailed deer and invasive wild pigs: Evidence for competition?

AbstractUnderstanding whether invasive and native species compete for shared resources where they co‐occur is essential for mitigating the negative impacts of invasive species on native ecosystems. Here, we examined how the presence and density of an invasive species, wild pigs (Sus scrofa), affect native white‐tailed deer (Odocoileus virginianus; hereafter, deer) on the Savannah River Site, SC, USA. We examined potential changes in deer areas of use, temporal overlap, and occupancy to evaluate the effects of wild pig occurrence and density on deer space use, diel activity, and co‐occurrence with wild pigs across 9 months during 2018 and 2019. Wild pig density had the strongest effect on deer space use in high‐ and moderate‐use areas. Declines in deer space use in response to wild pig density were most pronounced in March and October 2018 and April 2019 for females, while male space use declined in response to wild pig density in October and December 2018. Both species were largely nocturnal with high overlap in diel activity across months. Deer occupancy responses to wild pig density varied across months, with negative responses in May and October 2018 and positive responses in July 2018 and April 2019. Deer and wild pigs co‐occurred at 30%–59% of camera stations across months, with broadscale co‐occurrence patterns being unaffected by changes in shared cover or wild pig occurrence. Overall, our results suggest that deer make fine‐scale behavioral adjustments to avoid wild pigs, providing evidence that competition is likely occurring even where wild pig density is relatively low. Such fine‐scale behavioral plasticity in deer appears to mitigate the costs of competition with wild pigs and may be a mechanism enabling long‐term co‐existence of deer and wild pigs. Our study provides novel insight on the complexities of spatiotemporal relationships between invasive wild pigs and native deer and suggests that the negative effects of interactions between deer and wild pigs may be more pronounced when deer life history needs are particularly demanding. In areas where eradication of invasive wild pigs may be impossible, maintaining low wild pig densities may help mitigate, but may not eliminate, the negative effects of wild pigs on deer.

Estimating preharvest density, adult sex ratio, and fecundity of white-tailed deer using noninvasive sampling techniques.

Adult sex ratio and fecundity (juveniles per female) are key population parameters in sustainable wildlife management, but inferring these requires abundance estimates of at least three age/sex classes of the population (male and female adults and juveniles). Prior to harvest, we used an array of 36 wildlife camera traps during 2 and 3 weeks in the early autumn of 2016 and 2017, respectively. We recorded white‐tailed deer adult males, adult females, and fawns from the pictures. Simultaneously, we collected fecal DNA (fDNA) from 92 20 m × 20 m plots placed in 23 clusters of four plots between the camera traps. We identified individuals from fDNA samples with microsatellite markers and estimated the total sex ratio and population density using spatial capture–recapture (SCR). The fDNA‐SCR analysis concluded equal sex ratio in the first year and female bias in the second year, and no difference in space use between sexes (fawns and adults combined). Camera information was analyzed in a spatial capture (SC) framework assuming an informative prior for animals’ space use, either (a) as estimated by fDNA‐SCR (same for all age/sex classes), (b) as assumed from the literature (space use of adult males larger than adult females and fawns), or (c) by inferring adult male space use from individually identified males from the camera pictures. These various SC approaches produced plausible inferences on fecundity, but also inferred total density to be lower than the estimate provided by fDNA‐SCR in one of the study years. SC approaches where adult male and female were allowed to differ in their space use suggested the population had a female‐biased adult sex ratio. In conclusion, SC approaches allowed estimating the preharvest population parameters of interest and provided conservative density estimates.

Methylation of avpr1a in the cortex of wild prairie voles: effects of CpG position and polymorphism.

DNA methylation can cause stable changes in neuronal gene expression, but we know little about its role in individual differences in the wild. In this study, we focus on the vasopressin 1a receptor (avpr1a), a gene extensively implicated in vertebrate social behaviour, and explore natural variation in DNA methylation, genetic polymorphism and neuronal gene expression among 30 wild prairie voles (Microtus ochrogaster). Examination of CpG density across 8 kb of the locus revealed two distinct CpG islands overlapping promoter and first exon, characterized by few CpG polymorphisms. We used a targeted bisulfite sequencing approach to measure DNA methylation across approximately 3 kb of avpr1a in the retrosplenial cortex, a brain region implicated in male space use and sexual fidelity. We find dramatic variation in methylation across the avrp1a locus, with pronounced diversity near the exon–intron boundary and in a genetically variable putative enhancer within the intron. Among our wild voles, differences in cortical avpr1a expression correlate with DNA methylation in this putative enhancer, but not with the methylation status of the promoter. We also find an unusually high number of polymorphic CpG sites (polyCpGs) in this focal enhancer. One polyCpG within this enhancer (polyCpG 2170) may drive variation in expression either by disrupting transcription factor binding motifs or by changing local DNA methylation and chromatin silencing. Our results contradict some assumptions made within behavioural epigenetics, but are remarkably concordant with genome-wide studies of gene regulation.

Space Use Strategies and Nuptial Color in European Green Lizards

Abstract The conspicuous colors found in many lizards transfer information about their owner’s characteristics that are relevant to mating and social systems. Female European Green Lizards (Lacerta viridis) have been shown to prefer males with high ultraviolet (UV) throat reflectance. Additionally, components of throat patch color (such as UV chroma and brightness) have been shown to be condition-dependent and to signal relative head size and health status. In this study, we investigated whether or not different components of male nuptial color and other relevant traits were associated with characteristics of male space use during the reproductive season at two different locations. In Site 1, lizard density was two times higher, territory size was one third as large, and spatial overlap between territories was about half as large as in Site 2. Males at Site 1 showed movement patterns consistent with a mix of territorial and floater individuals, with floaters exhibiting greater throat brightness. Those mal...

Sexual fidelity trade-offs promote regulatory variation in the prairie vole brain.

Individual variation in social behavior seems ubiquitous, but we know little about how it relates to brain diversity. Among monogamous prairie voles, levels of vasopressin receptor (encoded by the gene avpr1a) in brain regions related to spatial memory predict male space use and sexual fidelity in the field. We find that trade-offs between the benefits of male fidelity and infidelity are reflected in patterns of territorial intrusion, offspring paternity, avpr1a expression, and the evolutionary fitness of alternative avpr1a alleles. DNA variation at the avpr1a locus includes polymorphisms that reliably predict the epigenetic status and neural expression of avpr1a, and patterns of DNA diversity demonstrate that avpr1a regulatory variation has been favored by selection. In prairie voles, trade-offs in the fitness consequences of social behaviors seem to promote neuronal and molecular diversity.

Effects of population density on corticosterone levels of prairie voles in the field

High population density is often associated with increased levels of stress-related hormones, such as corticosterone (CORT). Prairie voles (Microtus ochrogaster) are a socially monogamous species known for their large population density fluctuations in the wild. Although CORT influences the social behavior of prairie voles in the lab, the effect of population density on CORT has not previously been quantified in this species in the field. We validated a non-invasive hormone assay for measuring CORT metabolites in prairie vole feces. We then used semi-natural enclosures to experimentally manipulate population density, and measured density effects on male space use and fecal CORT levels. Our enclosures generated patterns of space use and social interaction that were consistent with previous prairie vole field studies. Contrary to the positive relationship between CORT and density typical of other taxa, we found that lower population densities (80 animals/ha) produced higher fecal CORT than higher densities (240/ha). Combined with prior work in the lab and field, the data suggest that high prairie vole population densities indicate favorable environments, perhaps through reduced predation risk. Lastly, we found that field animals had lower fecal CORT levels than laboratory-living animals. The data emphasize the usefulness of prairie voles as models for integrating ecological, evolutionary, and mechanistic questions in social behavior.

Mating effort and space use of an alpine ungulate during the rut

In ungulates, the rut generally leads to increased intra and interpopulation movements for males. Because movements induce energetic costs and missed feeding opportunities, they could be an indication of male mating effort. We studied space use of 44 male mountain goats (Oreamnos americanus) from three neighboring subpopulations in southeast Alaska, during the rut from 2005 to 2008. Using mixed models and an information theoretic approach with AIC, we analyzed the relationships between individual traits of males and their space use. We found no indication of breeding migration between subpopulations. Distances between individual seasonal ranges were not related to any individual trait. Daily movements, home range sizes, and total distance traveled during the rut did not vary with mass or age of individuals. As such, effects of individual traits on male space use during the rut appear weak and observed space use patterns do not support any of the main mating effort hypotheses.

Badger (Taxidea taxus) Resource Selection and Spatial Ecology in Intensive Agricultural Landscapes

American badgers (Taxidea taxus) are a prairie obligate species, but badger resource selection and space use is poorly understood, particularly east of the Mississippi River where anthropogenic land uses have replaced most native prairie. We assessed badger multi-scale resource selection and space use in intensive agricultural areas in Illinois and Ohio. We predicted that badgers would select for pasture and prairie, and higher elevations, and riparian areas because these habitats likely favor burrowing and foraging. Conversely, badgers should avoid cropland, roads, and forest at both spatial scales because these habitats may limit burrowing and foraging and potentially increase mortality risk. We also predicted annual male space use would increase with age and be greater than females because of age-related dominance and polygynous mating. We used radiolocations from 18 (11 females, seven males) and five (two females, three males) badgers in Illinois and Ohio, respectively, to estimate space use and multi-spatial scale resource selection. Within study areas, badgers strongly selected for cropland and higher elevations, and a lesser extent upland forest and pasture, but avoided roads and riparian areas. Landcover selection within home ranges varied by study area, but generally, badgers strongly selected for pasture, cropland, prairie, or higher elevation. Median annual 95% fixed kernel areas of Illinois badgers were greater (W8 = 16.00, P = 0.007) for males than females, and most males appeared to overlap two to three females during the breeding season. We suggest, although our study areas were highly fragmented agricultural landscapes, badgers appeared to select land cover types similar to native prairie, which provided burrowing and foraging opportunities. However, because prairie and pasture were relatively limited, badgers used expansive (x̄ = 20.0 ± 34.4 km2) home ranges to meet life requirements. Therefore, degradation and fragmentation of limiting resources may limit badger population growth in our study areas and should be considered for future management.

Influences of mating strategy on space use of Arizona gray squirrels

Space use frequently differs between sexes and may reflect differences in parental investment and limiting resources. We examined Arizona gray squirrels (Sciurus arizonensis) from April 2007 to December 2008 to determine effects of mating strategy on patterns of home-range size and overlap. Home ranges were large compared to those of congeners, suggesting an environment with low availability and predictability of resources, and differed by sex and season. Females maintained smaller home ranges overlapped more by males than females; overlap by male home ranges increased during the breeding season. Males had larger home ranges that overlapped females more than males; home-range size and overlap of both sexes increased during the breeding season. Additionally, male Arizona gray squirrels appear to respond to the distribution of females by enlarging home ranges to maximize proportion of females overlapped. Consequently, Arizona gray squirrels conform to theoretical predictions, with female space use influenced by access to food and male space use influenced by access to mates.

The Round‐Eared Sengi and the Evolution of Social Monogamy: Factors that Constrain Males to Live with a Single Female

AbstractAnimal dispersion in space and time results from environmental pressures, and affects the outcome of a species’ social organization. When females are solitary, males may either roam or be pair‐living. We studied possible environmental influences affecting the social organization of the round‐eared sengi (Macroscelides proboscideus) in a semi‐desert in South Africa, using trapping and radio‐tracking across 2.5 yr. Adult sex ratios did not deviate from 1:1 and we found no indication of sexual dimorphism in body mass. Females maintained exclusive areas, which had little overlap (<4%) with neighbouring females (NF), and males overlapped predominately only with the home range of single females. Generally, inter‐ and intra‐sexual overlap with neighbouring individuals was low (3–6%) for both sexes, indicating territoriality and pair‐living. Pairs were perennial and territories were maintained year‐round. However, males generally maintained much larger areas than females, which were sensitive to population density. Male space use appeared to be primarily limited by the presence of neighbouring males. Female home ranges were smaller‐sized despite changes in population density, possibly for energetic efficiency. Some paired males attempted to take over widowed females, but shifted back to their original home range following the intrusion of an un‐paired male. We conclude that social monogamy is the predominant social organization in round‐eared sengis in a semi‐desert that may have resulted from females living solitarily in small exclusive territories, balanced sex ratios, and from a low variation of body mass between males.

SEX DIFFERENCES IN SPACE USE OF CHIRICAHUA FOX SQUIRRELS

Sex differences in reproductive investment influence space use patterns of many animals. In polygynous mammals, male space use reflects distribution of females and female space use reflects relative distribution of food. We used radiotelemetry to examine seasonal patterns of home-range size, overlap, and distance traveled by male and female Chiricahua fox squirrels (Sciurus nayaritensis chiricahuae) from 2002 to 2003. Male and female home-range and core-area size varied little between nonmating and mating seasons. Female core areas had a greater percentage overlap by males than by females during mating and nonmating seasons. Males traveled farther in the mating season and females showed little variation between seasons. Extreme spatial and temporal fluctuations of food experienced by Chiricahua fox squirrels may result in space use patterns that differ from those of tree squirrels living in forests with a greater abundance of food.