Seasonal Activity Variations Research Articles

Camera traps reveal seasonal variation in activity and occupancy of the Alpine mountain hare Lepus timidus varronis

Mountain hare is a cold‐adapted species threatened by climate change, but despite its emblematic nature, our understanding of the causes of population decline remains limited. Camera traps are increasingly used in ecology as a tool for monitoring animal populations at large spatial and temporal scales. In mountain environments where field work is constrained by difficult access and harsh conditions, camera traps constitute a promising tool for surveying rare and elusive species such as the mountain hare. Our study explored the use of camera traps as a tool for studying seasonal habitat occupancy and daily activity patterns of the mountain hare, in order to carry out long‐term monitoring of populations. We installed 46 camera traps along elevation gradients in the Mont‐Blanc massif (France) from January 2018 to June 2022. We measured habitat variables at each camera trap site in order to define vegetation composition and habitat structure. We performed multi‐season and single‐season occupancy models to respectively describe habitat occupancy of the mountain hare throughout the year and identify the environmental variables influencing mountain hare presence during the breeding season. Mountain hares occupy coniferous forest in winter, and then switch to mixed areas of shrubland and grassland above treeline in spring and the beginning of summer. In spring, occupancy probability of the mountain hare increases with relative cover of mixed low shrub and herbaceous layer (i.e. the 10–40 cm vegetation layer), suggesting a link to food resources and protection from predation. Our results also confirm the nocturnal and crepuscular activity of the mountain hare during the breeding season, and strictly nocturnal activity in winter. Our results demonstrate the efficiency of camera traps as tools for monitoring mountain hare habitat occupancy in mountain environments and underline the importance of diverse habitat mosaics for the preservation of the species.

Spatiotemporal Niche Separation among Passeriformes in the Halla Mountain Wetland of Jeju, Republic of Korea: Insights from Camera Trap Data.

This study analyzed 5322 camera trap photographs from Halla Mountain Wetland, documenting 1427 independent bird sightings of 26 families and 49 species of Passeriformes. Key observations include morning activities in Cyanoptila cyanomelana and Horornis canturians and afternoon activity in Muscicapa dauurica and Phoenicurus auroreus. Wetlands were significantly preferred (P_i = 0.398) despite their smaller area, contrasting with underutilized grasslands (P_i = 0.181). Seasonal activity variations were notable, with overlap coefficients ranging from 0.08 to 0.81 across species, indicating diverse strategies in resource utilization and thermoregulation. Population density was found to be a critical factor in habitat usage, with high-density species showing more consistent activity patterns. The study's results demonstrate the ecological adaptability of Passeriformes in the Halla Mountain Wetland while highlighting the limitations of camera trapping methods. These limitations include their fixed field of view and intermittent recording capability, which may not fully capture the spectrum of complex avian behaviors. This research underlines the need for future studies integrating various methodologies, such as direct observation and acoustic monitoring, to gain a more comprehensive understanding of avian ecology.

Comparative Diurnal Activity Patterns of Merops Leschenaulti and Merops Orientalis at Chittagong University Campus, Bangladesh

A study was conducted on the diurnal activity patterns of chestnut-headed bee-eater (Merops leschenaulti) and green bee-eater (Merops orientalis) at Chittagong University Campus, Bangladesh in the year 2015. Six major activities (perching, flying, calling, feeding, diving, and preening) were recorded for both species during the study period. The two bee-eater species were observed to spend their maximum (M. leschenaulti: 37.63%; M. orientalis: 35.95%) time in perching, whereas the minimum time spent by M. leschenaulti was observed in diving (1.76%) and by M. orientalis was in feeding (2.17%). They were more active during 15:00 - 17:00 h (M. leschenaulti: 27.34%; M. orientalis: 27.23%) than other diurnal time blocks. Two species spent their highest (M. leschenaulti: 14.71%; M. orientalis: 14.00%) time performing different activities in June and the lowest (M. leschenaulti: 2.71%; M. orientalis: 3.46%) in January. Both bee-eaters were mostly (M. leschenaulti: 56.58%; M. orientalis: 53.07%) active in monsoon than in other seasons. The similar activity patterns between two bee-eater species could be influenced by similar lifestyles associated with their close taxonomic relationship. A number of ecological factors, such as temperature, humidity and precipitation could influence the daily, monthly and seasonal variations in activities. Bangladesh J. Zool. 51(2): 175-190, 2023

Seasonal variation in activity and nearshore habitat use of Lake Trout in a subarctic lake

BackgroundIn lake ecosystems, predatory fish can move and forage across both nearshore and offshore habitats. This coupling of sub-habitats, which is important in stabilizing lake food webs, has largely been assessed from a dietary perspective and has not included movement data. As such, empirical estimates of the seasonal dynamics of these coupling movements by fish are rarely quantified, especially for northern lakes. Here we collect fine-scale fish movement data on Lake Trout (Salvelinus namaycush), a predatory cold-water fish known to link nearshore and offshore habitats, to test for seasonal drivers of activity, habitat use and diet in a subarctic lake.MethodsWe used an acoustic telemetry positioning array to track the depth and spatial movements of 43 Lake Trout in a subarctic lake over two years. From these data we estimated seasonal 50% home ranges, movements rates, tail beat activity, depth use, and nearshore habitat use. Additionally, we examined stomach contents to quantify seasonal diet. Data from water temperature and light loggers were used to monitor abiotic lake conditions and compare to telemetry data.ResultsLake Trout showed repeatable seasonal patterns of nearshore habitat use that peaked each spring and fall, were lower throughout the long winter, and least in summer when this habitat was above preferred temperatures. Stomach content data showed that Lake Trout acquired the most nearshore prey during the brief spring season, followed by fall, and winter, supporting telemetry results. Activity rates were highest in spring when feeding on invertebrates and least in summer when foraging offshore, presumably on large-bodied prey fish. High rates of nearshore activity in fall were associated with spawning. Nearshore habitat use was widespread and not localized to specific regions of the lake, although there was high overlap of winter nearshore core areas between years.ConclusionsWe provide empirical demonstrations of the seasonal extent to which a mobile top predator links nearshore and offshore habitats in a subarctic lake. Our findings suggest that the nearshore is an important foraging area for Lake Trout for much of the year, and the role of this zone for feeding should be considered in addition to its traditional importance as spawning habitat.

Physical Activity And Screen Time Patterns During The Covid-19 Pandemic: The Role Of School Format.

Schools and communities across the United States shifted between virtual and in-person formats and reduced recreational offerings throughout the 2020-2021 school year due to widespread COVID-19 infection. Early cross-sectional studies indicate children’s physical activity (PA) decreased during the pandemic, but variation may be seen according to school format and seasonal changes in behavior. Purpose: The purpose of this study was to longitudinally assess changes in PA and screen time (ST) behaviors throughout one year of the COVID-19 pandemic and according to changes in school format. Methods: Parents of children ages 6-17y were recruited via email and social media. Most participants (57%) lived in the Midwestern region of the United States. The survey included questions about school format, home characteristics, child PA, child ST, child sleep habits, and parental support of PA. Initial data were collected in November 2020 with follow-up surveys in February, May, and August 2021. Children were first classified according to school format in each season then further grouped based on longitudinal changes in school format (i.e., in-person all year vs. remote to in-person, etc.). PA and ST behaviors were compared by season and school format using repeated measures ANOVA. Results: Overall, children achieved 60 minutes of PA on fewer days in winter (2.4 ± 0.3 days; p < 0.001; n = 176) than compared to fall (3.7 ± 0.3 days; n = 175), spring (3.8 ± 0.3 days; n = 141), and summer (3.8 ± 0.3 days; n = 112). Longitudinal analysis (n = 61) showed that PA was consistently highest among students attending school fully in-person and lowest among students attending remotely, though school format differences did not reach statistical significance. Non-school ST did not differ by season or school format but tended to be highest in winter and amongst students attending school remotely. Conclusion: In general, children demonstrated healthier lifestyle behavior patterns when attending school in-person than when attending school remotely. Seasonal variation in activity followed the expected pattern with the lowest PA in winter. These results provide a unique opportunity to evaluate lifestyle behaviors by school format throughout the year and suggest that students exhibit healthier behavior patterns when school occurs in person.

Camera traps reveal overlap and seasonal variation in the diel activity of arboreal and semi-arboreal mammals

Our study aimed to investigate seasonal variation in the activity of arboreal and semi-arboreal mammals and investigate their overlap in temporal activity, as well temporal shifts in activity because of behavioural interference. In our camera trapping study in a fragmented landscape in south-eastern Australia, a total of ten arboreal and semi-arboreal species were found, with 35,671 independent observations recorded over 6517 camera trap nights. All species were found to be nocturnal; however, a notable number of daytime observations were made for several species (i.e. brown antechinus, Antechinus stuartii; sugar glider, Petaurus breviceps; bush rat, Rattus fuscipes; brown rat, Rattus norvegicus). Seasonal variations in diel activity were observed through an increase in crepuscular activity in spring and summer for antechinus, sugar gliders, brown rats, brushtail possums, Trichosurus vulpecula and ringtail possums, Pseudocheirus peregrinus. Diel activity overlap between species was high, that is 26/28 species comparisons had overlap coefficients (Δ) > 0.75. The species pair with the least amount of overlap was between southern bobucks, Trichosurus cunninghami and brown antechinus (Δ4 = 0.66). The species pair with the most overlap was between the native sugar glider and introduced brown rat (Δ4 = 0.93). When comparing the activity of sugar gliders in sites with low and high abundance of brown rats, sugar gliders appear to shift their activity relative to the brown rats. Similarly, behavioural interference was also observed between antechinus and sugar gliders, and when comparing sites of low and high abundance of sugar glider, antechinus had a shift in activity. Our work provides some of the first quantification of temporal patterns for several of the species in this study, and the first for a community of arboreal and semi-arboreal mammals. Our results indicate that some shifts in behaviour are potentially occurring in response to behavioural interference, allowing for coexistence by means of temporal partitioning.

Seasonal variations of serotonin in the visual system of an ant revealed by immunofluorescence and a machine learning approach.

Hibernation, as an adaptation to seasonal environmental changes in temperate or boreal regions, has profound effects on mammalian brains. Social insects of temperate regions hibernate as well, but despite abundant knowledge on structural and functional plasticity in insect brains, the question of how seasonal activity variations affect insect central nervous systems has not yet been thoroughly addressed. Here, we studied potential variations of serotonin-immunoreactivity in visual information processing centres in the brain of the long-lived ant species Lasius niger. Quantitative immunofluorescence analysis revealed stronger serotonergic signals in the lamina and medulla of the optic lobes of wild or active laboratory workers than in hibernating animals. Instead of statistical inference by testing, differentiability of seasonal serotonin-immunoreactivity was confirmed by a machine learning analysis using convolutional artificial neuronal networks (ANNs) with the digital immunofluorescence images as input information. Machine learning models revealed additional differences in the third visual processing centre, the lobula. We further investigated these results by gradient-weighted class activation mapping. We conclude that seasonal activity variations are represented in the ant brain, and that machine learning by ANNs can contribute to the discovery of such variations.

Temporal Preference of Eurasian Lynx (Lynx lynx) in a Highland Forest in Northwestern Anatolia in Relation to Other Medium and Large Mammal Species

In this study, we aimed to determine the daily activity patterns and seasonal activity variations of the Eurasian lynx in different habitats (forests and open lands) in a geographical region where there are relatively few data on its ecological characteristics. Survey effort totaled 10 102 camera trap days, with 24 camera trap stations covering an area of approximately 650 km2. Our results showed no significant differences in the habitat preference of the lynx throughout the entire study area or between seasons. The crepuscular and nocturnal activity preferences of the lynx were similar to those of the wolf, red fox, and the European hare. The lynx's daily activity pattern peaked during 20:00–22:00 and 04:00–06:00 hours, and did not show significant variation between seasons. Kernel density estimation was used in order to reveal the temporal overlap of other carnivore and herbivore species with the lynx. The highest temporal overlap (coefficient of overlapping: 0.90) was seen with the European hare. Our findings also indicated higher temporal overlaps with the wolf, red fox, wild boar, and brown bear, and lower overlaps with the red deer, Southwest Asian badger, and Martes spp., which improved understanding of their interactions and co-existence with the lynx.

B-PO05-014 A RETROSPECTIVE STUDY OF SEASONAL VARIABILITY OF CARDIAC ELECTROPHYSIOLOGY IN THE RABBIT HEART

Rabbits are an important animal model for the study of cardiac electrophysiology and are suitable for analyzing mechanisms of cardiac arrhythmias. Rabbits are known to have seasonal variation in activity, behavior, and breeding; however, there are few data related to seasonal variation in electrophysiological parameters in the rabbit heart. To determine if there is significant seasonal variation in cardiac electrophysiology of the New Zealand White (NZW) rabbit heart. Male NZW rabbit hearts (N = 55) were purchased from an approved vendor and housed on a 12:12 hr light:dark cycle. Hearts were Langendorff-perfused for simultaneous optical mapping of Vm and Ca2+ with voltage-sensitive (RH237) and calcium-sensitive (Rhod2-AM) indicators, respectively. Data were collected from 2012-2016 and retrospectively analyzed. We defined the seasons meteorologically: December-February as winter, March-May as spring, June-August as summer and September-November as autumn. All data were collected while pacing at a constant cycle length of 300 ms. Retrospective data revealed seasonal variability in the action potential duration (APD) and in the calcium transient duration (CaTD). For summer compared to spring and autumn, APD50 (121.1 ± 11 vs. 137 ± 19.8 and vs. 135.3 ± 11.3 ms, p < 0.01 for both) and APD80 (151.1 ± 11.7 vs. 166.4 ± 17.6 and vs. 163.5 ± 11.9 ms, p < 0.01 for both) were significantly shorter, but not different from winter. For summer compared to spring, CaTD50 (123.8 ± 5.5 vs. 137.7 ± 13.2 ms, p < 0.01) and CaTD80 (162.8 ± 6.1 vs. 178.4 ± 16.9 ms, p = 0.11) were shorter. There was not significance difference in Vm-Ca2+ coupling (i.e., CaTD - APD) between seasons. APD and CaTD are significantly shorter in the summer months of isolated rabbit hearts. These data may provide insight into seasonal patterns of arrhythmia in humans, but should also be considered with regard to experimental rigor and reproducibility.

Occurrence and hazard assessment of natural radioactivity in drinking water in South Lebanon.

This study is intended to assess the natural radioactivity in the drinking water in the southern region of Lebanon and to determine its suitability for human consumption. In this context, activity concentrations for gross alpha, gross beta, 238U, 234U, and radon from selected drinking water sources, wells, and springs and the corresponding tap water, in the area under investigation, were determined during both the wet and the dry seasons. The maximum recorded activities of gross alpha, gross beta, and radon measured using liquid scintillation counter were found to be 374.6 ± 11.5mBq L-1 for gross alpha, 418 ± 12mBq L-1 for gross beta, and 42,900 ± 370mBq L-1 for radon. Whereas, alpha spectroscopy analysis for uranium content showed maximum activities of 53.7 ± 2.1mBq L-1 for 238U and 55.9 ± 2.3mBq L-1 for 234U. Significant seasonal activity variation between wet and dry season was noticed only in gross alpha concentrations. In addition, significant variation between sources and tap water was recorded only in radon concentrations. Whereas, no significant variation was noted in radioactivity concentrations in waters from springs and those from wells. In contrast to all sampled locations, the annual effective dose of only one sampled well (Aitaroun) exceeded the WHO individual dose criterion (IDC) level of 100 µSv year-1 and recorded an annual effective dose of 170 µSv year-1, 103 µSv year-1, and 127 µSv year-1 for infants, children, and adults, respectively.

Activity patterns of tayra (Eira barbara) across their distribution

Abstract Species’ activity patterns are driven by the need to meet basic requirements of food, social interactions, movement, and rest, but often are influenced by a variety of biotic and abiotic factors. We used camera-trap data to describe and compare the activity patterns of the relatively poorly studied tayra (Eira barbara) across 10 populations distributed from the south of Mexico to the north of Argentina, and attempted to identify biotic or abiotic factors that may be associated with variation in level of diurnality. In a subset of sites we also aimed to document potential seasonal variation in activity. We used a kernel density estimator based on the time of independent photographic events to calculate the proportion of diurnal, crepuscular, and nocturnal activity of each population. Tayras were mostly active during diurnal periods (79.31%, 759 records), with a lower proportion of crepuscular activity (18.07%, 173 records) yet we documented some variation in patterns across the 10 study areas (activity overlap coefficient varied from Δ 4 = 0.64 to Δ 1 = 0.95). In northern localities, activity peaked twice during the day (bimodal) with most activity ocurring in the morning, whereas closer to the geographical equator, activity was constant (unimodal) throughout the day, peaking at midday: activity either was unimodal or bimodal in southern localities. Despite investigating multiple potential abiotic and biotic predictors, only latitude was associated with variation in the proportion of diurnal activity by tayras across its range, with increased diurnal activity closer to the equator. Seasonal comparisons in activity showed a tendency to reduce diurnality in dry versus rainy seasons, but the pattern was not consistently significant. This is the most comprehensive description of tayra activity patterns to date, and lends novel insight into the potential flexibility of the species to adapt to local conditions.

Estimation of spatiotemporal trends in bat abundance from mortality data collected at wind turbines.

Renewable energy sources, such as wind energy, are essential tools for reducing the causes of climate change, but wind turbines can pose a collision risk for bats. To date, the population‐level effects of wind‐related mortality have been estimated for only 1 bat species. To estimate temporal trends in bat abundance, we considered wind turbines as opportunistic sampling tools for flying bats (analogous to fishing nets), where catch per unit effort (carcass abundance per monitored turbine) is a proxy for aerial abundance of bats, after accounting for seasonal variation in activity. We used a large, standardized data set of records of bat carcasses from 594 turbines in southern Ontario, Canada, and corrected these data to account for surveyor efficiency and scavenger removal. We used Bayesian hierarchical models to estimate temporal trends in aerial abundance of bats and to explore the effect of spatial factors, including landscape features associated with bat habitat (e.g., wetlands, croplands, and forested lands), on the number of mortalities for each species. The models showed a rapid decline in the abundance of 4 species in our study area; declines in capture of carcasses over 7 years ranged from 65% (big brown bat [Eptesicus fuscus]) to 91% (silver‐haired bat [Lasionycteris noctivagans]). Estimated declines were independent of the effects of mitigation (increasing wind speed at which turbines begin to generate electricity from 3.5 to 5.5 m/s), which significantly reduced but did not eliminate bat mortality. Late‐summer mortality of hoary (Lasiurus cinereus), eastern red (Lasiurus borealis), and silver‐haired bats was predicted by woodlot cover, and mortality of big brown bats decreased with increasing elevation. These landscape predictors of bat mortality can inform the siting of future wind energy operations. Our most important result is the apparent decline in abundance of four common species of bat in the airspace, which requires further investigation.

Influence of some abiotic factors on the activity patterns of trapdoor spiders, scorpions and camel spiders in a central South African grassland

Trapdoor spiders (Araneae: Mygalomorphae), scorpions (Scorpiones) and camel spiders (Solifugae) were collected by pitfall trapping from an undisturbed grassland area within the Free State National Botanical Gardens, with the aim of analysing the effects of rainfall, temperature and lunar incidence on their activity patterns. During the study a total of 8109 non-acarine arachnids were collected, of which Mygalomorphae, Solifugae and Scorpiones represented only 5.04% (n = 409). Mygalomorph spiders (n = 195) were represented by four families and five species, namely Ancylotrypa dreyeri (Hewitt, 1915) (Cyrtaucheniidae), Stasimopus oculatus Pocock, 1897 and S. minor Hewitt, 1915 (Ctenizidae), Segregara sylvestris (Hewitt, 1925) (Idiopidae) and Calommata meridionalis Fourie, Haddad and Jocqué, 2011 (Atypidae). Scorpions (n = 71) were represented by two buthid species, Uroplectes triangulifer (Thorell, 1876) and U. carinatus (Pocock, 1890). Solifugae (n = 153) were represented by Solpugema coquinae orangica (Hewitt, 1919) and Solpugassa sp. (Solpugidae). Rainfall and temperature were the main factors influencing seasonal variations in activity, with lunar incidence having no detectable effect. Uroplectes triangulifer and Solpugema coquinae orangica were the only species active during late winter and early spring, prior to the first significant rains in mid-spring. After emerging, populations of most species rapidly increased to a peak before declining again.

Quantifying bee assemblages and attractiveness of flowering woody landscape plants for urban pollinator conservation.

Urban and suburban landscapes can be refuges for biodiversity of bees and other pollinators. Public awareness of declining pollinator populations has increased interest in growing plants that provide floral resources for bees. Various publications and websites list “bee-friendly” plants, but such lists are rarely based on empirical data, nor do they emphasize flowering trees and shrubs, which are a major component of urban landscapes. We quantified bee visitation to 72 species of flowering woody landscape plants across 373 urban and suburban sites in Kentucky and southern Ohio, USA, sampling and identifying the bee assemblages associated with 45 of the most bee-attractive species. We found strong plant species effects and variation in seasonal activity of particular bee taxa, but no overall differences in extent of bee visitation or bee genus diversity between native and non–native species, trees and shrubs, or early-, mid-, and late-season blooming plants. Horticulturally-modified varieties of Hydrangea, Prunus, and Rosa with double petals or clusters of showy sterile sepals attracted few bees compared to related plants with more accessible floral rewards. Some of the non-native woody plant species bloomed when floral resources from native plants were scarce and were highly bee-attractive, so their use in landscapes could help extend the flowering season for bees. These data will help city foresters, landscape managers, and the public make informed decisions to create bee–friendly urban and suburban landscapes.

Urban Intensities. The Urbanization of the Iberian Mediterranean Coast in the Light of Nighttime Satellite Images of the Earth

The contribution shares the approach of critical urban studies that have conceptualized urbanization more as a process than as a sum of spatial forms. Thus, the contribution studies the urbanization process not only from the point of view of the physical occupation of land but also considers changes in the intensity of the uses of space. To fulfill this aim, the new sources of nocturnal satellite images are particularly useful. These allow us to observe the intensity of urban uses both in terms of their distribution over space and their recurrence over time. The research focuses on the Iberian Mediterranean coast and permits the verification of the intensity of the urban uses of the space for the whole of this area and their seasonal variations throughout the year. The source of the study are the nighttime satellite images of the Earth for the 2012–2017 period from the NASA SNPP satellite equipped with the VIIRS-DNB instrument. By establishing a threshold of urban light the research shows that those districts with the greatest extensions of urban light do not necessarily correspond with the most densely populated areas. Similarly the absence of urban light does not necessarily indicate the absence of urban uses. Finally, the variations of intensity of light prove to be a good indicator of seasonal variations of activity in tourist areas.

Chemical Diversity of Sands Within the Linear and Barchan Dunes of the Bagnold Dunes, Gale Crater, as Revealed by APXS Onboard Curiosity

AbstractAlpha Particle X‐ray Spectrometer (APXS) results for Phase 2 of the Bagnold Dunes campaign, focusing on the linear dunes, complement those from Phase 1 (barchan dunes) and add to our understanding of active Martian dune systems. This work highlights both compositional similarities and differences across the dune field. The concentration of elements associated with mafic minerals in coarser grains and along active ripple crests, previously identified in the barchan dunes, highlights differences in Martian and terrestrial weathering, transport, and sorting processes. Concentration of a Cr‐Ti mineral phase within the linear sands is identified. The inactive ripple fields are geochemically similar to soil, while active ripple fields are similar to sands. Inferred dust content (S + Cl + Zn concentrations), derived from APXS analyses, provide geochemical confirmation of current and seasonal activity variations, within the barchan and linear dunes, as well as revealing a continuum between inactive soils and active sands.

The endogenous activity patterns of Africa’s smallest terrestrial mammal, the pygmy mouse (Mus minutoides)

The endogenous rhythmicity of the locomotor activity and subsequent entrainment by light cycles of the pygmy mouse (Mus minutoides A. Smith, 1834) was investigated under laboratory-controlled conditions. Seasonal trapping in the field was used to assess the predominant activity phase in their natural habitat, and determine whether seasonal variation in activity occurs in the field. Mus minutoides were subjected to a series of light cycles starting with a 12 h light (L) : 12 h dark (D) cycle (2 weeks) to determine whether they entrain their activity patterns to light cues, after which they were maintained in constant darkness (3 weeks) and the endogenous rhythm allowed to free run; the tau for each animal’s endogenous activity rhythm was then calculated. This was followed by another 12 h L : 12 h D cycle (2 weeks) before the cycle was inverted to 12 h D : 12 h L (2 weeks) to assess the rate of re-entrainment. The animals were then exposed to long (16 h L : 8 h D) and short (8 h L : 16 h D) photoperiods for a 6-week period under each lighting regime. Changes in foraging behaviour and body mass were recorded throughout the study. Mus minutoides is strictly nocturnal in both the laboratory and the field, it caches food in its nest, and it cannot be trapped during the winter months in this environment.

Temporal niche switching in Arabian oryx (Oryx leucoryx): Seasonal plasticity of 24 h activity patterns in a large desert mammal

The Arabian oryx, a moderately large mammal that inhabits a harsh desert environment, has been shown to exhibit seasonal variations in activity and inactivity patterns. Here we analyzed the continuous year-round activity patterns of twelve free-roaming Arabian oryx under natural conditions from two varying desert environments in Saudi Arabia using abdominally implanted activity meters. We simultaneously recorded weather parameters at both sites to determine whether environmental factors are responsible for temporal niche switching as well as the seasonal structuring and timing of this behavioural plasticity. Our results demonstrate that Arabian oryx undergo temporal niche switching of 24h activity patterns at a seasonal level and exhibit distinct nocturnal/crepuscular activity during summer, diurnal activity during winter and intermittent patterns of behaviour during the transitional seasons of autumn and spring. In addition, the oryx exhibited inter- and intra-seasonal variations in the temporal budgeting of 24h activity patterns. Strong relationships with both photoperiod and ambient temperatures were found and in some instances suggested that increasing ambient temperatures are a primary driving force behind seasonal shifts in activity patterns. These adaptive patterns may be dictated by the availability of food and water, which in turn are strongly influenced by seasonal climate variations. Overall, the adaptive responses of free-roaming Arabian oryx in such harsh and non-laboratorial conditions provide a framework for comparing wild populations as well as aiding conservation efforts.

The Ecology of Stress: linking life-history traits with physiological control mechanisms in free-living guanacos.

BackgroundProviding the context for the evolution of life-history traits, habitat features constrain successful ecological and physiological strategies. In vertebrates, a key response to life’s challenges is the activation of the Stress (HPA) and Gonadal (HPG) axes. Much of the interest in stress ecology is motivated by the desire to understand the physiological mechanisms in which the environment affects fitness. As reported in the literature, several intrinsic and extrinsic factors affect variability in hormone levels. In both social and non-social animals, the frequency and type of interaction with conspecifics, as well as the status in social species, can affect HPA axis activity, resulting in changes in the reproductive success of animals. We predicted that a social environment can affect both guanaco axes by increasing the secretion of testosterone (T) and Glucocorticoid (GCs) in response to individual social interactions and the energetic demands of breeding. Assuming that prolonged elevated levels of GCs over time can be harmful to individuals, it is predicted that the HPA axis suppresses the HPG axis and causes T levels to decrease, as GCs increase.MethodsAll of the data for individuals were collected by non-invasive methods (fecal samples) to address hormonal activities. This is a novel approach in physiological ecology because feces are easily obtained through non-invasive sampling in animal populations.ResultsAs expected, there was a marked adrenal (p-value = .3.4e−12) and gonadal (p-value = 0.002656) response due to seasonal variation in Lama guanicoe. No significant differences were found in fecal GCs metabolites between males/females*season for the entire study period (p-value = 0.2839). Despite the seasonal activity variation in the hormonal profiles, our results show a positive correlation (p-value = 1.952e−11, COR = 0.50) between the adrenal and gonadal system. The marked endocrine (r2 = 0.806) and gonad (r2 = 0.7231) response due to seasonal variation in male guanaco individuals highlights the individual’s energetic demands according to life-history strategies. This is a remarkable result because no inhibition was found between the axes as theory suggests. Finally, the dataset was used to build a reactive scope model for guanacos.DiscussionGuanacos cope with the trade-off between sociability and reproductive benefits and costs, by regulating their GCs and T levels on a seasonal basis, suggesting an adaptive role of both axes to different habitat pressures. The results presented here highlight the functional role of stress and gonad axes on a critical phase of a male mammal’s life—the mating period—when all of the resources are at the disposal of the male and must be used to maximize the chances for reproductive success.

Seasonal depletion of resources intensifies trophic interactions in subarctic freshwater fish communities

Summary Climate change in recent decades has resulted in an increase in both the density and diversity of consumers in subarctic freshwater ecosystems. Despite this, harsh winter conditions in the region limit productivity and may serve as a bottleneck driving trophic interactions within the fish community, potentially determining the outcome of climate change for resident biota. However, due to the difficulties in sampling during winter months, few studies have assessed seasonal variation in the ecological interactions between native and range‐expanding species in subarctic regions. We examined seasonal variation in activity, diet (stomach content) and resource use (δ13C and δ15N stable isotope ratios) of two fishes: the resident cold‐water‐adapted European whitefish (Coregonus lavaretus L.) and the range‐expanding cool‐water‐adapted ruffe (Gymnocephalus cernua L.) in lakes with low and high consumer density. Results were contrasted with seasonal availability of benthic and pelagic resources and indirect measures of individual fitness, that is condition, growth and estimated lipid content (muscle elemental C : N ratio) of both species. The effects of fish density were apparent in both the diet and resource use of whitefish, which altered their diet and displayed reduced stomach fullness during winter in high‐density lakes. This was associated with an overall reduction in whitefish growth, condition and estimated lipid content in high‐density lakes, which was especially pronounced during winter. Ruffe utilised a greater proportion of profundal resources than whitefish in both summer and winter, potentially exploiting a vacant niche. Ruffe maintained condition and lipid reserves throughout the winter, highlighting the potential for further northward range expansion of the species. Winter acts as a seasonal bottleneck in subarctic lakes, but assumptions that this bottleneck primarily selects against warmer‐water‐adapted invasive species such as ruffe may be too restrictive. The effects of seasonal resource depletion on fish condition and invertebrate density were most severe in lakes with a high density of fish, and in these conditions, the cold‐water‐adapted resident whitefish was most adversely affected.