Larger antelopes are sensitive to heat stress throughout all seasons but smaller antelopes only during summer in an African semi-arid environment

A Summer Heat Wave Reduced Activity, Heart Rate, and Autumn Body Mass in a Cold-Adapted Ungulate

AbstractHeat waves are becoming more frequent across the globe and may impose severe thermoregulatory challenges for endotherms. Heat stress can induce both behavioral and physiological responses, which may result in energy deficits with potential fitness consequences. We studied the responses of reindeer (Rangifer tarandus tarandus), a cold-adapted ungulate, to a record-breaking heat wave in northern Finland. Activity, heart rate, subcutaneous body temperature, and body mass data were collected for 14 adult females. The post-heat wave autumn body masses were then analyzed against longitudinal body mass records for the herd from 1990 to 2021. With increasing air temperature during the day, reindeer became less active and had reduced heart rate and increased body temperature, reflecting both behavioral and physiological responses to heat stress. Although they increased activity in the late afternoon, they failed to compensate for lost foraging time on the hottest days (daily mean temperature ≥20°C), and total time active was reduced by 9%. After the heat wave, the mean September body mass of herd females (69.7±6.6 kg, n=52) was on average 16.4% ± 4.8% lower than predicted (83.4±6.0 kg). Among focal females, individuals with the lowest levels of activity during the heat wave had the greatest mass loss during summer. We show how heat waves impose a thermoregulatory challenge on endotherms, resulting in mass loss, potentially as a result of the loss of foraging time. While it is well known that environmental conditions affect large herbivore fitness indirectly through decreased forage quality and limited water supply, direct effects of heat may be increasingly common in a warming climate.

Between hunter and climate: the effects of hunting and environmental change on fecal glucocorticoid metabolite levels in two sympatric ungulate species in the Ruaha-Rungwa ecosystem, Tanzania

Understanding the drivers of animal population decline is a key focus of conservation biologists. Anthropogenic activities such as hunting have long been established as potentially detrimental to a population's persistence. However, environmental perturbations such as increased temperature variability, exacerbated by climate change, can also have important effects on animal populations. Animals can respond to these challenges by adjusting both their behavior and physiology. We measured fecal glucocorticoid metabolites (FGMs) of common impala (Aepyceros melampus) and greater kudu (Tragelaphus strepsiceros), both currently in stable populations, to examine effects of hunting, forage availability, daily variability in temperature and group size on their physiological stress response. The study was conducted across two adjacent protected areas, (i) one non-hunted area (Ruaha National Park; RNP) and (ii) one area used for trophy hunting (Rungwa Game Reserve; RGR). Both impala and kudu had significantly higher FGM levels in the area that allows hunting, while FGM levels decreased with increasing forage availability and increasing daily temperature. Moreover, impala (but not kudu) had lower FGM levels with larger group sizes. Our results indicate that the management regime can significantly alter the physiological state of wild ungulate populations. We also highlight the importance of considering the combined effects of anthropogenic, environmental and social contexts when studying the stress response of wild populations. Our results emphasize the value of protected areas and continued monitoring of hunting quota in order to maintain ungulate populations that are less vulnerable to population declines.

Grouping behaviour and activity patterns of impala (Aepyceros melampus) in a nutrient –rich and a nutrient-poor savanna in Tanzania

African savannas are broadly categorised into nutrient-rich and nutrient-poor according to soil nutrient availability and precipitation. Soil nutrients limit plant growth in the nutrient-rich savannas, leading to little plant biomass of high nutrient concentrations. In the nutrient-poor savannas soil nutrients are depleted before plant growth ceases, resulting in large production of nutrient-poor plant biomass. Impala (Aepyceros melampus), are medium-sized antelopes occurring in both savannas, but they face feeding challenges in the nutrient-poor savannas because of high energy requirements. Activity patterns of impala are well studied, but few studies compared savannas with differing soil nutrients and animal communities. I used the scanning methods to study impala activities in a nutrient-rich savanna, the Serengeti National Park, and a nutrient-poor savanna, the Mikumi National Park in Tanzania, during the wet and dry seasons. Impala are gregarious and mixed feeders, utilising grasses during the wet season, switching to browsing during the dry season, making them good candidates for comparing savannas and seasons. The impala formed bigger groups in Mikumi during the wet season splitting during the dry season. Grazing time was higher in the wet season than in the dry season in Serengeti, but did not differ between the seasons in Mikumi. Browsing time was longer in Mikumi than Serengeti during the dry season, and longer in Serengeti than Mikumi during the wet season. Resting time was longer in Serengeti than Mikumi during the wet season, while walking time was longer in Mikumi than Serengeti during the dry season. Family groups spent longer time resting than bachelor groups in both sites. The study shows obvious differences in grouping and activity patterns of impala between the sites and the seasons. Further studies are recommended to explore the influence of savanna and season on grouping behaviour and activity patterns of herbivores.

Spatially restricted occurrence and low abundance as key tools for conservation of critically endangered large antelope in West African savannah

The effective conservation of mammals on the brink of extinction requires an integrated socio-ecological approach, yet the updated ecological knowledge of species remains fundamental. This study brings spatiotemporal behaviour, population structure, age-specific survival rates, and population size estimate of the Western Derby eland (WDE) in the Niokolo Koba National Park (NKNP), Senegal, investigated during dry seasons 2017 and 2018. WDE was strongly localised in the core area of NKNP (< 5%), active throughout the day with the highest peak in the hottest daytime, with a mean group size 7.6 ± SE 8.9. The adult sex ratio was female-biased and showed low annual adult male survival rates. The population consisted of high proportion of juveniles, whilst adults did not exceed 40%. The estimated population density was 0.138 WDE/km² (± 0.0102) and estimated size 195 WDE in NKNP (CI95 from 54 to 708 individuals). Findings highlighted that the WDE population has potential to expand in the NKNP, due to an underutilized capacity. The age-specific vital rates indicate adult males as the most vulnerable; suggesting either an increase in the large predators' population, livestock encroachment pressure, and/or poaching. Findings imply that targeted monitoring with science-based interpretation may bring forward strong conservation solutions to the protected area management decision-makers.

Mammal Persistence Along Riparian Forests in Western India Within a Hydropower Reservoir 55 Years Post Construction

While the negative impacts of dam construction on downstream river stretches and riparian forests are well studied, the status of wildlife presence and persistence in upstream reservoir deltas is virtually unknown. We investigated the drivers of terrestrial mammal occupancy and persistence along riparian forests of Koyna reservoir in western India 55 years after its construction. We adopted a catchment-wide field design grounded in the river continuum concept and sampled different stream orders within the reservoir. Camera traps, nested in an occupancy modeling framework, were deployed across 72 riparian sites and replicated for four seasons across all stream types. We recorded a total of nineteen species of terrestrial mammals during the study period. Multi-season occupancy models revealed three key patterns of mammal persistence: (a) ungulates were more frequently photo-captured in riparian forests; gaur and wild pig had the highest proportions of the total sampled area (0.84 ± 0.12 SE; 0.77 ± 0.07 SE, respectively); (b) small-sized ungulates were more vulnerable to local extinction than large-bodied ungulates; extinction probability was highest for barking deer (0.59 ± 0.07) and lowest for sambar (0.15 ± 0.07); and (c) distance from stream played major roles in determining mammal detection. Riparian forests are fundamentally important to ecosystem functioning and biodiversity conservation, and using the data from this study, managers can plan to sustain high mammal persistence along riparian forests at Koyna reservoir or similar Indian reserves. Further, our robust sampling approach, grounded in the terrestrial-riverine continuum concept, can be applied globally to understand species assemblages, aiding in multi-landscape and wildlife management planning.

Different environmental requirements of female and male Siberian ibex, Capra sibirica

In sexually dimorphic species, males and females may select different habitat for greater fitness. However, the key factors that play a leading role between sexes in habitat selection are still poorly understood. In this paper, we investigated the possible causes of the differences in habitat preference between male and female Siberian ibex (Capra sibirica) living in the Tianshan Mountains (China). Using the Maximum entropy model, we found that the ruggedness and elevation of the terrain were the most important factors affecting habitat selection in Siberian ibex. Females preferred the most rugged terrain to increase the security of their young and themselves, while males favored moderately rugged terrain to provide sufficient safety from predators, and availability of suitable forage simultaneously. Females used a wider variety of elevations to search for newly emerged vegetation for its higher nutritional value, while males preferred more elevated slopes to avoid the higher temperatures and greater presence of biting insects found at the lower elevations. In addition, females were associated more with rivers due to their higher water demands. The differences in habitat selection between Siberian ibex males and females depend on multiple considerations, but only a limited number of key factors determine their actual distribution.

Contrasting capabilities of two ungulate species to cope with extremes of aridity

Southern Africa is expected to experience increased frequency and intensity of droughts through climate change, which will adversely affect mammalian herbivores. Using bio-loggers, we tested the expectation that wildebeest (Connochaetes taurinus), a grazer with high water-dependence, would be more sensitive to drought conditions than the arid-adapted gemsbok (Oryx gazella gazella). The study, conducted in the Kalahari, encompassed two hot-dry seasons with similar ambient temperatures but differing rainfall patterns during the preceding wet season. In the drier year both ungulates selected similar cooler microclimates, but wildebeest travelled larger distances than gemsbok, presumably in search of water. Body temperatures in both species reached lower daily minimums and higher daily maximums in the drier season but daily fluctuations were wider in wildebeest than in gemsbok. Lower daily minimum body temperatures displayed by wildebeest suggest that wildebeest were under greater nutritional stress than gemsbok. Moving large distances when water is scarce may have compromised the energy balance of the water dependent wildebeest, a trade-off likely to be exacerbated with future climate change.

Perspectives on biometeorological research on the African continent

Since the first issue of the International Journal of Biometeorology in 1957, a total of 135 papers have reported on research in or of African countries. The majority of these have been on topics of animal biometeorology (36%), and the greatest proportion (24%) are situated in Nigeria. There has been a considerable increase in papers on African biometeorology since 2011, with those from this past decade accounting for 58% of all African papers in the journal. This occurs concurrent to an increase in the total number of papers published in the journal, driven by a move to the Editorial Manager system. While 66% of the papers on African biometeorology in the journal are authored by at least one person with an affiliation in the African continent, only 15 African countries are represented in the total authorship. As much of the African continent is projected to experience climatic changes exceeding the global mean, as much of the region is involved in animal and plant farming, and as seasonally-fluctuating and climatically affected diseases are common place, this low representation of work in Africa is surprising. This points to the need for greater awareness among African researchers of the discipline of biometeorology, greater involvement of African biometeorologists in International Society of Biometeorology and Commission meetings, and the inclusion of a greater number of African academics in the review process. This would be beneficial to the Society in increasing diversity and encouraging a more cosmopolitan engagement, and to the recognition of scientific development in African countries.

Mapping Shade Availability and Use in Zoo Environments: A Tool for Evaluating Thermal Comfort

For many species in zoos, particularly megafauna vulnerable to heat stress, shade is a key environmental resource. However, shade availability has received comparatively less attention than other aspects of the zoo environment. In this study, we share a simple low-cost approach that we applied to document shade availability across 33 zoo enclosures. We then combined these assessments with behavioral observations of enclosure use and shade-seeking behavior during summer months in a case study focused on Sichuan takin (Budorcas taxicolor tibetana) (n = 3), a large cold-adapted bovid. Behavioral observations were conducted before and after installation of a shade sail for the takin. Results indicated that shade availability varied widely across zoo enclosures, with the percent of shaded space ranging from 85 % to 22 % across enclosures during summer months. Shade was a dynamic resource and increased throughout the year and fluctuated across the day, with the least shade available midday. Takin showed general preferences for shaded areas near the walls of their enclosure but were observed using newly available shade from the shade sail after its installation. These accessible methods can be easily applied to assess shade within existing enclosures, evaluate enclosure modifications, and provide guidance for the design of new enclosures.

Seasonal variation in the foraging activity of desert argali (Ovis ammon) in Mongolia

Debate remains whether energy maximization or time minimization strategies best explain foraging in ungulates. It has also been hypothesized that the capacity of an animal to dissipate body heat regulates animal activity. We investigated these hypotheses while measuring the daily activity of desert argali (Ovis ammon (Linnaeus,1758)) for 12 months and relating the activity pattern to environmental seasonality. We found significant seasonal cycles in argali activity, with the greatest proportion of daytime in winter spent foraging and the greatest proportion of daytime in summer spent bedding. Consistent with an energy maximization strategy, argali reduced all behaviors during the winter in favor of foraging, compensating for the increased energy demands of winter at a time of low forage quality. Consistent with a time minimization strategy, argali in summer significantly reduced foraging and spent more time bedding in shaded areas to avoid hyperthermia due to high ambient temperatures. Both optimal foraging and heat dissipation can be used to explain the observed foraging pattern. Foraging behavior in argali is best described by the extent to which the animals schedule their activities to meet their physiological demands, the way these demands are affected by environmental variables, and the time that is available to accomplish them.

Large herbivore assemblages in a changing climate: incorporating water dependence and thermoregulation

The coexistence of different species of large herbivores (ungulates) in grasslands and savannas has fascinated ecologists for decades. However, changes in climate, land‐use and trophic structure of ecosystems increasingly jeopardise the persistence of such diverse assemblages. Body size has been used successfully to explain ungulate niche differentiation with regard to food requirements and predation sensitivity. But this single trait axis insufficiently captures interspecific differences in water requirements and thermoregulatory capacity and thus sensitivity to climate change. Here, we develop a two‐dimensional trait space of body size and minimum dung moisture content that characterises the combined food and water requirements of large herbivores. From this, we predict that increased spatial homogeneity in water availability in drylands reduces the number of ungulate species that will coexist. But we also predict that extreme droughts will cause the larger, water‐dependent grazers as wildebeest, zebra and buffalo–dominant species in savanna ecosystems – to be replaced by smaller, less water‐dependent species. Subsequently, we explore how other constraints such as predation risk and thermoregulation are connected to this two‐dimensional framework. Our novel framework integrates multiple simultaneous stressors for herbivores and yields an extensive set of testable hypotheses about the expected changes in large herbivore community composition following climate change.

Spatial and temporal behavioural responses of wild cattle to tropical forest degradation

Identifying the consequences of tropical forest degradation is essential to mitigate its effects upon forest fauna. Large forest-dwelling mammals are often highly sensitive to environmental perturbation through processes such as fragmentation, simplification of habitat structure, and abiotic changes including increased temperatures where the canopy is cleared. Whilst previous work has focused upon species richness and rarity in logged forest, few look at spatial and temporal behavioural responses to forest degradation. Using camera traps, we explored the relationships between diel activity, behavioural expression, habitat use and ambient temperature to understand how the wild free-ranging Bornean banteng (Bos javanicus lowi) respond to logging and regeneration. Three secondary forests in Sabah, Malaysian Borneo were studied, varying in the time since last logging (6–23 years). A combination of generalised linear mixed models and generalised linear models were constructed using >36,000 trap-nights. Temperature had no significant effect on activity, however it varied markedly between forests, with the period of intense heat shortening as forest regeneration increased over the years. Bantengs regulated activity, with a reduction during the wet season in the most degraded forest (z = -2.6, Std. Error = 0.13, p = 0.01), and reductions during midday hours in forest with limited regeneration, however after >20 years of regrowth, activity was more consistent throughout the day. Foraging and use of open canopy areas dominated the activity budget when regeneration was limited. As regeneration advanced, this was replaced by greater investment in travelling and using a closed canopy. Forest degradation modifies the ambient temperature, and positively influences flooding and habitat availability during the wet season. Retention of a mosaic of mature forest patches within commercial forests could minimise these effects and also provide refuge, which is key to heat dissipation and the prevention of thermal stress, whilst retention of degraded forest could provide forage.

Effect of season and high ambient temperature on activity levels and patterns of grizzly bears (Ursus arctos)

Understanding factors that influence daily and annual activity patterns of a species provides insights to challenges facing individuals, particularly when climate shifts, and thus is important in conservation. Using GPS collars with dual-axis motion sensors that recorded the number of switches every 5 minutes we tested the hypotheses: 1. Grizzly bears (Ursus arctos) increase daily activity levels and active bout lengths when they forage on berries, the major high-energy food in this ecosystem, and 2. Grizzly bears become less active and more nocturnal when ambient temperature exceeds 20°C. We found support for hypothesis 1 with both male and female bears being active from 0.7 to 2.8 h longer in the berry season than in other seasons. Our prediction under hypothesis 2 was not supported. When bears foraged on berries on a dry, open mountainside, there was no relationship between daily maximum temperature (which varied from 20.4 to 40.1°C) and the total amount of time bears were active, and no difference in activity levels during day or night between warm (20.4–27.3°C) and hot (27.9–40.1°C) days. Our results highlight the strong influence that food acquisition has on activity levels and patterns of grizzly bears and is a challenge to the heat dissipation limitation theory.