Biology Letters最新文献

Functional specialization of the brain hemispheres has been observed across the animal kingdom, with the left hemisphere being associated with positive emotions while the right hemisphere is associated with negative emotions. In vertebrates, contralateral eye use is indicative of which brain hemisphere is being used for processing and so may therefore reveal affective state. Using a within-subjects design, we investigated whether lateralized eye use could be used as a non-invasive welfare indicator in captive-bred lizards (Pogona vitticeps) housed in standard or enriched enclosures for four weeks. Eye use was recorded during basking, a key maintenance behaviour. We found that when lizards were housed in standard enclosures (an environment associated with reduced welfare) they exhibited significantly greater use of their left eye (right brain hemisphere) compared to when they were housed in enriched enclosures (an environment associated with improved welfare). These findings suggest that the negative affective state induced by housing conditions is reflected in lateralized eye use, making this a promising, non-invasive tool for assessing animal welfare that is likely to be of value across vertebrate species.

In this article, we consider the extent to which wildlife tourism in China has become a nodal point where human-animal interactions have been consistently shaped and reshaped by the multiple layers of naturecultural complexity. We do this by investigating Chinese visitors' evaluation of animal welfare as they apply to red and giant pandas at the Chengdu Research Base of Giant Panda Breeding (Panda Base). A survey of Chinese visitors indicated generally positive perceptions of the welfare conditions of pandas at Panda Base. Visitors largely viewed the institution as providing excellent care to pandas, reflecting a high degree of public trust in the organization. While red pandas were perceived to experience slightly better welfare conditions, visitor concern and attention focussed more heavily on giant pandas-possibly due to their iconic status. This study investigates how species status and environmental visibility influence Chinese visitors' perceptions of animal welfare at a major wildlife tourism site. It highlights how iconic animals such as the giant panda are often assumed to receive excellent care, while lesser-known species like the red panda invite more diverse interpretations-thus revealing a potential symbolic bias in public welfare judgements. These findings suggest a symbolic bias in welfare judgements, shaped not only by observable enclosure features but also by the animals' cultural significance in the native culture.

Leafcutter farming systems are ant-fungus mutualisms whose ecological success hinges on differentiation of fungal hyphae into swollen cells called gongylidia that ants consume. While gongylidium cells are unique signatures of coevolved crop domestication, their cell biology is poorly understood. Each gongylidium cell contains a large vacuole that is thought to protectively store plant degradation enzymes that ants ingest and vector unharmed in faecal droplets back to the fungus. We hypothesized that enzyme storage requires gongylidium vacuoles to have distinct levels of pH and reactive oxygen species (ROS) compared to the vacuoles of undifferentiated hyphae that likely degrade cellular waste. We used live-cell fluorescence microscopy of fungal isolates with targeted probes to first show that both cell types had vacuoles with lower pH than the surrounding cytosol. In contrast, while hyphal vacuoles stored ROS, gongylidium vacuoles excluded these potentially harmful molecules. These findings suggest derived cellular adaptations in a mutualistic fungus where gongylidia protect ant-vectored enzymes through specialized subcellular ROS compartmentalization.

Marine heat waves (MHW) are a leading cause of death for stony corals, and it is reasonable to expect that a record-breaking MHW would negatively impact coral communities; 2023-2024 provided a test of this assertion in St John, US Virgin Islands, where an intense MHW brought temperatures of 30.6°C and degree-heating weeks of 23.23°C-weeks. On reefs where coral cover has been low for decades, the 2023/2024 MHW did not have discernable effects on coral cover. Nonetheless, there was a trend between 2023 and 2024 for mean coral cover to decline by small absolute (≤ 3%), but large relative (13-27%) amounts, with these changes affecting multiple genera and perturbing coral assemblages. These trends are eclipsed by the massive changes that have affected these coral communities since 1987; the 2023/2024 MHW was the latest in a series of disturbances transitioning these reefs to low coral cover. This MHW did not statistically depress coral cover, but it changed coral assemblages, intensifying the ecological perils of rarity, extirpation and perhaps local extinction.

The mango stem borer Batocera rufomaculata is a large beetle (Cerambycidae) exhibiting a high intra-specific variation in adult body size because of differing environmental conditions during larval growth. Previous studies revealed that smaller individuals can fly longer distances than larger ones before reaching exhaustion, a surprising fact considering that the cost of transport is expected to increase with decreased body size. We tested the flight propensity and metabolic rhythms of these beetles as a function of sex and body size. The intrinsic flight-initiating behaviour and the daily fluctuations in metabolic rate (MR) were measured over 48 h in closed arenas and in metabolic chambers, respectively. Beetles displayed a strong circadian pattern of nocturnal activity in both locomotion and MR. Smaller conspecifics were significantly more active both metabolically and behaviourally than larger ones with sex having no effect on the size-related difference. The results suggest a stronger innate drive to disperse by flight in smaller conspecifics, providing a behavioural-physiological link between environmental conditions during the larval growth period and the dispersal potential of the adults.

Land conversion is a widespread form of environmental change that can alter infection dynamics in wildlife by modifying host immune defence. Such effects may be compounded by seasonal variation in resources and reproduction and differ among members of a host community, yet the combined effects of habitat, season and species identity on wildlife immunity remain poorly understood. We tested within- and across-species effects of land conversion and seasonality on immunity in Neotropical bats by quantifying haematological markers of physiological stress and inflammation. We sampled seven species across a large forest preserve and smaller nearby forest fragment in northern Belize during the dry and wet seasons. Using phylogenetic generalized linear mixed models, we tested overall effects of habitat and season and quantified per-species impacts. Total leukocyte counts and neutrophil-to-lymphocyte ratios showed no overall habitat or seasonal effects but displayed strong species-specific responses to these predictors. In contrast, the systemic inflammation response index was higher across species in the dry season and in the smaller fragment, suggesting poor health in unfavourable conditions. Species-specific effects did not align with diet guilds, indicating potential roles for finer-scale ecological traits. Our results highlight the complex, species-dependent effects of environmental change on wildlife immunity.

Publishing non-significant findings is essential for the progress of science. However, many of us forget that 'absence of evidence is not evidence of absence' and believe that a statistically non-significant result is evidence of no effect. Regrettably, and despite the null hypothesis being simple, elegant and often underpinned by evidenced or reasoned convictions, conventional p-value analysis can only argue against the null hypothesis, never in favour of it. Here, I provide a quick-and-easy guide to simple yet powerful statistical options available to biologists for investigating the absence of a meaningful effect, namely equivalence tests, confidence intervals and credible intervals; or the absence of any effect, namely likelihood ratios and Bayes factors. These approaches, supported by accessible software, allow biologists to draw direct conclusions about the null hypothesis.

Ground sloths were terrestrial megafauna that inhabited the Western Hemisphere. While they are inferred to have been browsers and grazers based on craniodental morphology, it is plausible that they performed a wide range of ecological functions, including seed dispersal, bioturbation and nutrient cycling. Understanding ground sloth ecology is challenging due to their enamel-free dentition, which poses limitations to palaeodietary methods, like stable isotope analysis, due to the increased probability of diagenesis in more porous tissues. Here, we conduct dental microwear texture analysis on Paramylodon harlani and Nothrotheriops shastensis specimens from the La Brea Tar Pits in southern California to compare these species to each other, to co-occurring megafauna and to modern analogues to clarify ground sloth dietary ecology. DMTA of P. harlani (i.e. low anisotropy and high complexity) and N. shastensis (i.e. low anisotropy and low complexity) suggests that P. harlani consumed significantly harder foods (e.g. tubers, roots, seeds, fruit pits) than N. shastensis. Findings underscore that these species were not functional replicates of each other or of co-occurring browsers and grazers (e.g. camels and bison). Considering the high degree of dietary overlap in extant folivorous sloths, the extinction of giant ground sloths represents a true loss of ecological function.

The Late Pleistocene was a time of global megafaunal extinctions that were particularly severe in North America. The continent lost many mammal taxa, but the validity of several remains ambiguous, including a high proportion of Cervidae taxa. Torontoceros hypogaeus is represented by a single specimen (ROMM75974) discovered in 1976 during excavation work for the Toronto subway in Canada. The species was described based on its unique antler morphology, but the variable nature of that trait and the species near absence in the fossil record leads to uncertainty concerning its systematic relationships. We used ancient DNA to clarify the taxonomic relationship and evolutionary history of T. hypogaeus. We performed mitochondrial and whole genome analyses with related cervids and showed that ROMM75974 has a close affinity, but relatively high divergence from Odocoileus sister species. While some ambiguity remains, ROMM75974 could represent a distinct Odocoileus species to be included in the list of extinct North American taxa. This unique population was likely adapted to open landscape, which was rapidly replaced with dense woodland in this region at the end of the Pleistocene, highlighting the role of climate change in the extinction of megafauna biodiversity at the end of the ice age.

Human activity has profoundly shaped the landscape of resources available to animals. While certain species, such as scavengers, are particularly adapted to exploit resources that fluctuate significantly over space and time, their responses to sudden human-induced changes in resources remain poorly understood. The COVID-19 lockdown offered a natural experiment to study these dynamics, as reduced human mobility abruptly decreased roadkill availability for scavengers. Here, we examined how reductions in roadkill affected the foraging behaviour of an avian facultative scavenger, the red kite (Milvus milvus). We hypothesized that with fewer carcasses available, red kites would decrease their use of roads for scavenging. GPS tracking data from 199 non-breeding individuals confirmed that red kites switched from actively selecting roads before the lockdown (2017-2019) to avoiding them during lockdown (2020), with the trend reversing again afterwards (2021-2023). Selection for areas with higher probability of anthropogenic feeding increased during lockdown and remained elevated afterwards. Our findings highlight that abrupt changes in human activity can drive rapid behavioural shifts in a generalist forager, with certain effects lasting for years after the change.