Home range size in the blue-eyed black lemur (Eulemur flavifrons): A comparison between dry and wet seasons

Consistency in Verreaux's sifaka home range and core area size despite seasonal variation in resource availability as assessed by Enhanced Vegetation Index (EVI)

Primates are adept at dealing with fluctuating availability of resources and display a range of responses to minimize the effects of food scarcity. An important component of primate conservation is to understand how primates adapt their foraging and ranging patterns in response to fluctuating food resources. Animals optimize resource acquisition within the home range through the selection of resource-bearing patches and choose between contrasting foraging strategies (resource-maximizing vs. area-minimizing). Our study aimed to characterize the foraging strategy of a folivorous primate, Verreaux's sifaka (Propithecus verreauxi), by evaluating whether group home range size varied between peak and lean leaf seasons within a seasonally dry tropical forest in Madagascar. We hypothesized that Verreaux's sifaka used the resource maximization strategy to select high-value resource patches so that during periods of resource depression, the home range area did not significantly change in size. We characterized resource availability (i.e., primary productivity) by season at Kirindy Mitea National Park using remotely-sensed Enhanced Vegetation Index data. We calculated group home ranges using 10 years of focal animal sampling data collected on eight groups using both 95% and 50% kernel density estimation. We used area accumulation curves to ensure each group had an adequate number of locations to reach seasonal home range asymptotes. Neither 95% home ranges nor 50% core areas differed across peak and lean leaf resource seasons, supporting the hypothesis that Verreaux's sifaka use a resource maximization strategy. With a better understanding of animal space use strategies, managers can model anticipated changes under environmental and/or anthropogenic resource depression scenarios. These findings demonstrate the value of long-term data for characterizing and understanding foraging and ranging patterns. We also illustrate the benefits of using satellite data for characterizing food resources for folivorous primates.

Effects of forest fragmentation on the dietary ecology and activity of a nocturnal lemur community in North West Madagascar

Deforestation and habitat fragmentation is the primary threat to primate populations. The primates that live within degraded and anthropogenically disturbed habitats typical of fragmented landscapes have to cope with lower availability of resources in comparison to primates in continuous, undisturbed forests. While some species are sensitive to forest fragmentation, some evidence exists to suggest that primates can alter their behavior and adapt to such changes, which enables their survival in suboptimal habitat. In this study, we assessed how forest fragmentation and its associated edge-effects impact the feeding ecology and activity levels of a nocturnal primate community in the Sahamalaza-Iles Radama National Park, North West Madagascar. From March 06, 2019 to May 17, 2022, we collected data on tree and invertebrate phenology at our study site, and feeding ecology and activity for 159 lemur individuals from four species. Fruit and flower availability varied significantly between continuous and fragmented forest, and between forest core and edge areas, with continuous forest exhibiting higher continuous fruit and flower availability. Lemur feeding ecology varied significantly too, as the feeding niches of all four species were significantly different between continuous and fragmented forest and between core and edge areas. However, lemur activity levels were mostly consistent among all forest areas. The results of this study suggest that nocturnal lemurs are able to adapt their dietary ecology in response to the available food sources within their habitat. Due to this flexible ecology and dietary plasticity, the lemurs do not need to significantly alter their behavior in different environments to fulfill their dietary needs. While nocturnal lemurs demonstrate adaptability and flexibility to degraded habitat, it is unclear how far this plasticity will stretch considering that Madagascar's forests are still being cleared at an alarming rate. Urgent conservation action is therefore needed to ensure the future of lemur habitat.

Linking changes in individual specialization and population niche of space use across seasons in the great evening bat (Ia io)

BACKGROUND

The niche breadth of an animal population comprises both within-individual and between-individual variation (individual specialization). Both components can be used to explain changes in population niche breadth, and this has been extensively investigated in dietary niche dimension studies. However, little is known about how changes in food resources or environmental factors across seasons affect changes in individual and population space use within the same population.

METHODS

In this study, we used micro-GPS loggers to capture the space use of individuals and of a population of the great evening bat (Ia io) in summer and autumn. We used I. io as a model to investigate how individual spatial niche breadth and spatial individual specialization affect changes in population niche breadth (home range and core area sizes) across seasons. Additionally, we explored the drivers of individual spatial specialization.

RESULTS

We found that the population home range and the core area of I. io did not increase in autumn when insect resources were reduced. Moreover, I. io showed different specialization strategies in the two seasons: higher spatial individual specialization in summer and lower individual specialization but broader individual niche breadth in autumn. This trade-off may maintain the dynamic stability of the population spatial niche breadth across seasons and facilitate the population response to changes in food resources and environmental factors.

CONCLUSIONS

Like diet, spatial niche breadth of a population also may be determined by a combination of individual niche breadth and individual specialization. Our work provides new insights into the evolution of niche breadth from the spatial dimension.

Seasonal Differences in the Encounter Rate of the Fat-Tailed Dwarf Lemur (Cheirogaleus medius) in the Transitional Forests of Northwest Madagascar: Implications for Reliable Population Density Assessment

Primate encounter rates often vary throughout the year due to seasonal differences in activity, ecology, and behaviour. One notably extreme behaviour is continuous hibernation. Although a rare adaptation in primates, the dwarf lemurs of Madagascar (genus Cheirogaleus) enter obligate hibernation each year during the dry season, after spending the wet season consuming high-energy foods. Whilst seasonal changes in activity in some Cheirogaleus populations are well-known, many species remain little-studied, and there is no specific information on their encounter rates, nor when they enter and emerge from hibernation. This uncertainty critically affects reliable calculation of population density estimates for these highly threatened lemurs. In this study, we assessed how encounter rates of the fat-tailed dwarf lemur (C. medius) vary seasonally in the transitional forests of the Sahamalaza-Iles Radama National Park, northwest Madagascar, during a 4-year period. We established a system of line transects (N = 60) throughout our study area, on which we conducted distance sampling of C. medius. We then used our distance sampling data to calculate encounter rate and population density data. We found encounter rates of C. medius to be significantly higher during the wet season compared with the dry season. Furthermore, encounter rates of C. medius were particularly low from May–August. These results provide some evidence to suggest the time period that C. medius hibernate in Sahamalaza-Iles Radama National Park. These findings underpin the importance of careful study design when surveying threatened species with seasonal differences in activity, such as those that hibernate. This study also demonstrates the importance of species-specific behavioural data for accurate population density assessment, which is required to inform conservation action.

The Influence of Environmental Variables on Home Range Size and Use in the Golden Snub-Nosed Monkey (Rhinopithecus roxellana) in Tangjiahe National Nature Reserve, China

Accurate descriptions of home ranges can provide important information for understanding animal ecology and behavior and contribute to the formulation of conservation strategies. We used the grid cell method and kernel density estimation (KDE) to estimate the home range size of golden snub-nosed monkeys (Rhinopithecus roxellana) in Tangjiahe National Nature Reserve. We also used Moran’s eigenvector maps analysis and variation partitioning to test the influence of environmental variables on home range use. The seasonal home range size was 15.4 km2 in spring, 11.6 km2 in summer, 13.7 km2 in autumn, and 15.6 km2 in winter, based on the grid cell method. The seasonal core area of 50% KDE was 9.86 km2 in spring, 5.58 km2 in summer, 7.20 km2 in autumn, and 4.23 km2 in winter. The environmental variables explained 63.60% of home range use intensity in spring, 72.21% in summer, 26.52% in autumn, and none in winter, and some environmental variables contributed to the spatial variation in home range use intensity. Water sources, tree density, and dominant trees of Chinese wingnut (Pterocarya stenoptera) were the important environmental factors determining home range use. These environmental factors require protection to ensure the survival of the golden snub-nosed monkey.

Group differences in feeding and diet composition of wild western gorillas

The ecological-constraints model posits that living in larger groups is associated to higher travel costs and reduced nutritional intake due to within-group feeding competition setting upper group size limits. While this is critical for frugivorous mammals, the model is less ubiquitous for folivores who feed on more abundant and evenly distributed food. The seasonally frugivorous diet of western gorillas (Gorilla gorilla) provides the opportunity to study the ecological-constraints model in the largest primate species. We investigated how two groups of western gorillas of differing sizes (N = 9, N = 15) in Central African Republic, responded to seasonal variation in fruit availability in terms of activity and diet. We used continuous focal animal sampling during periods of high (July–August 2011) and low (October 2011–January 2012) fruit availability, measured by monthly phenological scores. While diet diversity, resting and moving time did not differ between groups, overall the smaller group spent more time feeding than the larger group although this became less evident when fruit was more available. The smaller group was more frugivorous than the larger group. However, the larger group increased more steeply fruit consumption when fruit was more available, and incorporated more insects, young leaves and bark when fruit was less available, when compared to the smaller group. Up to a certain limit, the flexibility of large, seasonal frugivores to survive on a more folivorous diet may buffer the upper limit group size, suggesting deviation from the ecological-constraints model as in some folivores.

Seasonal variation in the behavioural ecology of samango monkeys (Cercopithecus albogularis schwarzi) in a southern latitude montane environment

Samango monkeys (Cercopithecus albogularis schwarzi) in the Soutpansberg Mountains, South Africa, experience a highly seasonal climate, with relatively cold, dry winters. They must show behavioural flexibility to survive these difficult conditions near the southern limit of the species' distribution and maintain the minimum nutritional intake they require. Through environmental monitoring and behavioural observations of a habituated group of samango monkeys, we explored how they adapted to the highly seasonal climate they experienced in the mountains. Our results indicated that the monkeys varied their foraging behaviours to account for changes in climate and daylight availability. The samangos increased their food intake in colder months, specifically leaves, likely due to an increased need for calories during winter to maintain body temperature. Samango monkeys have anatomical and physiological adaptations for digesting leaves, and these are likely important in explaining their ability to adapt to the broad range of climatic conditions they experience.

A Systematic Review of Within-Population Variation in the Size of Home Range Across Ungulates: What Do We Know After 50 Years of Telemetry Studies?

Studying the factors determining the sizes of home ranges, based on body mass, feeding style, and sociality level, is a long-standing goal at the intersection of ecology and evolution. Yet, how species-specific life history traits interact with different components of the landscape to shape differences in individual home ranges at within-population level has received much less attention. Here, we review the empirical literature on ungulates to map our knowledge of the relative effects of the key environmental drivers (resource availability, landscape heterogeneity, lethal and non-lethal risks) on the sizes of individual home ranges within a population and assess whether species' characteristics (body mass, diet, and social structure), account for observed variation in the responses of the sizes of individual home ranges to local environmental drivers. Estimating the sizes of home ranges and measuring environmental variables raise a number of methodological issues, which complicate the comparison of empirical studies. Still, from an ecological point of view, we showed that (1) a majority of papers (75%) supported the habitat productivity hypothesis, (2) the support for the influence of landscape heterogeneity was less pervasive across studies, (3) the response of cattle-type to variation in food availability was stronger than the response of moose-type, and (4) species-specific body mass or sociality level had no detectable effect on the level of support to the biological hypotheses. To our surprise, our systematic review revealed a dearth of studies focusing on the ecological drivers of the variation in the sizes of individual home ranges (only about 1% of articles that dealt with home ranges), especially in the later decade where more focus has been devoted to movement. We encourage researchers to continue providing such results with sufficient sample sizes and robust methodologies, as we still need to fully understand the link between environmental drivers and individual space use while accounting for life-history constraints.

Realized distribution patterns of crowned lemurs (Eulemur coronatus) within a human-dominated forest fragment in northern Madagascar

Due to the impact of anthropogenic activities on forest extent and integrity across Madagascar, it is increasingly necessary to assess how endangered lemur populations inhabiting human-dominated forest fragments can effectively sustain themselves ecologically. Our research addresses this concern by exploring how the distribution patterns of a small population of crowned lemurs (Eulemur coronatus), occupying a degraded forest fragment at Oronjia Forest New Protected Area in northern Madagascar, are impacted by the availability of key ecological and anthropogenic factors. We hypothesize that the distribution of E. coronatus within the fragment is limited by the availability of critical ecological resources and conditions and the intensity of anthropogenic features and activities. To examine this, we used MaxEnt to develop a species distribution model using presence-only occurrence records and 10 independent background covariates detailing the site's ecological and anthropogenic aspects. The results indicate that the realized distribution patterns of E. coronatus within human-dominated forest fragments are strongly associated with sections of forest that contain sparsely and sporadically distributed resources, such as freshwater and continuous hardwood vegetation. We conclude that the distribution of E. coronatus at Oronjia is shaped by their need to maximize foraging opportunities in a degraded forest landscape where they are subject to both environmental and anthropogenic stressors.

Lateralization in seven lemur species when presented with a novel cognitive task

OBJECTIVES

Asymmetrical behavior patterns are observed in many animal species, but the potential adaptive significance of lateralization and the evolutionary forces driving it remain unclear. Most laterality studies have focused on a single species, which makes interspecies comparisons difficult. The aim of this study was to examine differences in the strength and direction of lateralization in multiple lemur species when engaged in a standardized, novel cognitive task.

MATERIALS AND METHODS

We assessed laterality in seven lemur species at the Duke Lemur Center when using a novel puzzle-box. We recorded which hand opened the apparatus door and which hand picked up the food reward. We also recorded whether the mouth was used for either action instead of the hands. We then calculated handedness indices (HI), z-scores, and mouth-use rates.

RESULTS

Overall, 62% of individuals were more lateralized than chance. However, within-genera, there were relatively equal numbers of individuals with a left- or right-hand bias, which resulted in ambipreference at the genus level. The hand a lemur used on its first success in the task predicted its overall HI value, and the strength of lateralization increased as the number of successes increased. Varecia had significantly higher mouth-use rates than all other genera.

DISCUSSION

We found evidence of an individual learning trajectory in which the hand used on a lemur's first success was canalized as the preferred (and lateralized) hand, in support of the "cognitive simplicity" hypothesis. Individual variability in hand preference was high, which is consistent with previous research. Between-genera differences in mouth use appear to reflect species-specific feeding postures and differences in manual dexterity.

Spatiotemporal distribution of individuals as an indicator for the social system of Lepilemur sahamalaza

Primate social systems are highly diverse, complicating the classification of particularly elusive species that are difficult to observe. The spatial distribution of individuals over time is a critica lindicator for the social organization and long-term studies are important to establish patterns of social interactions. In recent years, species of the cryptic, nocturnal sportive lemurs of the genus Lepilemur were found to live in pairs in which a single male and a single female share and defend a mutual home range. The present study aimed to forward research into this underrepresented genus by determining the social organization and structure of the Sahamalaza sportive lemur, L. sahamalaza. We collected 773.15 hr of behavioral and GPS data during a period of 10 months (between 2015 and 2016) on 14 individuals: eight females and six males. There was no evidence of pair-specific home range use as intra- and intersexual home range overlap was high. No pattern of social interactions between focal individuals could be distinguished despite high range overlap. Individuals met and interacted infrequently, resulting in an interaction rate of 0.32 interactions/hr. Sleeping associations between adult individuals were never observed. While both sexes had access to multiple potential mating partners, range sizes or ranging distances did not increase in mating periods. Overall, the social system of Sahamalaza sportive lemurs exhibits aspects of a solitary social organization and structure with potential for the polygamous mating system. These findings underline the importance of detailed social ecology studies that can provide the basis for understanding potential environmental influences on social system variability of closely related species.

The Effects of Climate Seasonality on Behavior and Sleeping Site Choice in Sahamalaza Sportive Lemurs, Lepilemur sahamalaza

Temperature, rainfall, and resource availability may vary greatly within a single year in primate habitats. Many primate species show behavioral and physiological adaptations to this environmental seasonality, including changes to their diets and activity. Sahamalaza sportive lemurs (Lepilemur sahamalaza) inhabit the northwest of Madagascar and have been studied only during the dry, colder period of the year. We investigated potential effects of climate seasonality on this species by collecting behavioral data between October 2015 and August 2016, encompassing both the warmer wet and the colder dry seasons. We collected 773.15 hours of behavioral data on 14 individual sportive lemurs to investigate year-round activity budgets, ranging behavior, and sleeping site locations. Additionally we recorded temperature and rainfall data at our study site to describe the environmental conditions during the study period. The study individuals significantly decreased their time spent traveling and increased their time spent resting in the dry season compared to the wet season. Although home range size and path lengths did not differ over the study period, sleeping locations were significantly different between seasons as the lemurs focused on more confined areas in colder periods. Overall, the results indicate that Sahamalaza sportive lemur behavior varies with season, in line with reports for other primates.

Home range of reintroduced Chinese water deer in Nanhui East Shoal Wildlife Sanctuary of Shanghai, China

The Chinese water deer was once widely spread in Liaodong Peninsula, North China Plain and both banks of the Yangtze River and the Korean peninsula. Due to long-term environmental changes and influence of human development, its wild population in China has rapidly declined, both in abundance and distribution. As one of the native species in the history of Shanghai, Chinese water deer was introduced to Shanghai for captive breeding in 2006 and were released into the wild in 2010. The present study was conducted in Nanhui East Shoal Wildlife Sanctuary. The reintroduction of Chinese water deer was carried out separately in June and October 2010. So as to study the movement of the deer after release, 12 Chinese water deer (sex ratio 1 : 1) were tagged with radio-collars. We successfully used radio-telemetry to track 10 deer, and used the minimum convex polygon (MCP) and fixed kernel estimation (FKE) methods to calculate their home range. The results showed that using the MCP method, the mean home-range size of Chinese water deer was estimated to be 671 ha (range 245–1559 ha), while using the 95% FKE method, the mean was estimated to be 262 ha (range 43–435 ha). The mean home-range size of a buck was smaller than that of a doe by both MCP and FKE. The mean home-range size of an adult female was smaller than that of a subadult female. The largest seasonal home-range size (MCP, 275 ha) occurred during the winter of the first year, which then kept on shrinking in spring and summer. Home-range overlap was found among the home range of each individual. The mean overlap size was 303 ha. The mean overlap size was 135 ha in bucks, 422 ha in does and 270 ha between the buck and the doe. The study reflects that the seasonal food change is probably the main factor for the change of home-range size. Oestrus may also result in the enlargement of home range in winter. As an attempt to reintroduce large mammals to cities, we hope to provide useful experience for future wildlife management and conservation.

Lemurs and macaques show similar numerical sensitivity

We investigated the precision of the approximate number system (ANS) in three lemur species (Lemur catta, Eulemur mongoz, and Eulemur macaco flavifrons), one Old World monkey species (Macaca mulatta) and humans (Homo sapiens). In Experiment 1, four individuals of each nonhuman primate species were trained to select the numerically larger of two visual arrays on a touchscreen. We estimated numerical acuity by modeling Weber fractions (w) and found quantitatively equivalent performance among all four nonhuman primate species. In Experiment 2, we tested adult humans in a similar procedure, and they outperformed the four nonhuman species but showed qualitatively similar performance. These results indicate that the ANS is conserved over the primate order.

Aye-aye population genomic analyses highlight an important center of endemism in northern Madagascar

We performed a population genomics study of the aye-aye, a highly specialized nocturnal lemur from Madagascar. Aye-ayes have low population densities and extensive range requirements that could make this flagship species particularly susceptible to extinction. Therefore, knowledge of genetic diversity and differentiation among aye-aye populations is critical for conservation planning. Such information may also advance our general understanding of Malagasy biogeography, as aye-ayes have the largest species distribution of any lemur. We generated and analyzed whole-genome sequence data for 12 aye-ayes from three regions of Madagascar (North, West, and East). We found that the North population is genetically distinct, with strong differentiation from other aye-ayes over relatively short geographic distances. For comparison, the average FST value between the North and East aye-aye populations--separated by only 248 km--is over 2.1-times greater than that observed between human Africans and Europeans. This finding is consistent with prior watershed- and climate-based hypotheses of a center of endemism in northern Madagascar. Taken together, these results suggest a strong and long-term biogeographical barrier to gene flow. Thus, the specific attention that should be directed toward preserving large, contiguous aye-aye habitats in northern Madagascar may also benefit the conservation of other distinct taxonomic units. To help facilitate future ecological- and conservation-motivated population genomic analyses by noncomputational biologists, the analytical toolkit used in this study is available on the Galaxy Web site.