Ambient light can have a marked influence on the behavior of many species, particularly prey animals, where increased illumination may raise the risk of predation while offering limited advantages for activities such as foraging and mating. Katydids, which depend on species-specific acoustic signals for long-distance communication, are known to be sensitive to environmental conditions. However, the impact of ambient light on paleotropic katydids remains unexplored. The current study explored the effect of ambient light, temperature, and humidity on katydid assemblages at two locations, one in Northeast India and the other in the Western Ghats, over 5 years (2015-2020). We examined possible differences across seasons and between ecosystems at each site. A total of 537 encounters through psychoacoustic monitoring were used for the analysis. The results showed that temperature and humidity had no significant impact. Ambient light had a significant effect on katydid activity, with overall activity peaking near the waxing phase, thereby indicating a strong influence of light. Comparison between ecosystems showed contrasting results across sites, activity peak being more closely associated with the understorey in the Western Ghats and with grasslands in Northeast India. Although elevated light may increase predation risk, especially in open habitats, the consequent impact on the activity level of individual species varies. While previous studies explore the effect of sympatric signallers and predators, our study is the first to explore how the natural environment might affect the signaling activity of katydid assemblages in the Paleotropics.
Understanding the temporal niche of different carnivores and their interactions with humans is crucial for conservation research. This study aimed to investigate the activity patterns of the carnivore community and their responses to human activities in the common leopard (Panthera pardus) distribution area of the Luoxu White-lipped Deer Nature Reserve, Sichuan Province, China. From September 2019 to October 2020, camera traps were used to obtain data on seven different carnivores. Kernel density estimation and generalised linear models were used to study the temporal niche partitioning of these carnivores and their reactions to human and livestock activities. Among the three types of large carnivores, common leopards preferred daytime and twilight and showed limited activity at night; the grey wolf (Canis lupus) preferred daytime; and brown bears (Ursus arctos) favoured twilight and night. Mesocarnivores there were nocturnal. The alpine weasel (Mustela altaica), a small-sized carnivore, was diurnal. The staggered activity peaks among these carnivores indicated temporal niche partitioning, which presumably reduced direct interspecific competition. Furthermore, the relative abundance index 2 (RAI2) of certain species was associated with different environmental and biological factors across different time periods. Common leopards showed no association with elevation during daytime but exhibited avoidance of grey wolf habitats. During twilight, their RAI2 increased at higher elevations and was independent of grey wolf distribution. Brown bear activity was not associated with human presence during daytime but shifted at night to areas that had been used by humans throughout the day. The RAI2 of common leopards showed a negative correlation with distance to settlements. Grey wolf daytime RAI2 was positively correlated with the RAI2 of humans and horses during the same time period. These findings inform management decisions and conservation efforts for ecological communities threatened with human encroachment.
Aggressive mimicry is an ambush strategy observed in various animal taxa, including snakes, which use caudal luring (CL) to attract prey. CL involves cryptically colored snakes waving a conspicuous tail tip (CTT) to mimic worm-like invertebrates, luring prey that feeds on such organisms. This strategy is common among Viperidae, particularly in juveniles, which often exhibit ontogenetic shifts in diet (OSD) from ectothermic to endothermic prey. Although CL, CTT and OSD are assumed to be correlated, this relationship has never been empirically tested. This study investigated the origin and persistence of CL, CTT and OSD in Viperidae evolution, assessing their phylogenetic signal and testing for correlations. Data on the presence or absence of these traits were compiled from the literature, and phylogenetic comparative methods were used to measure phylogenetic signal, test correlations and reconstruct ancestral character states using parsimony and maximum likelihood. Results revealed strong phylogenetic signals for all three traits and significant correlations between each pair. Maximum likelihood reconstructions suggested that the ancestral Viperidae possessed CL, CTT, and OSD, while parsimony analyses indicated CL and CTT were present in the ancestor, but OSD was not. These findings support the hypothesis that CL, CTT and OSD are evolutionarily linked and have been integral to Viperidae since their origin. Despite being the most comprehensive study on these traits, significant gaps in viper natural history data were identified. This highlights the need for further descriptive ecological studies to enhance understanding of viperid biology and support broader macroevolutionary research.
The trade-off between protection and mobility is a central principle in functional ecology and is particularly relevant in terrestrial hermit crabs, which depend on gastropod shells for defense while potentially incurring locomotor costs. Under the trade-off hypothesis, heavier or asymmetric shells are expected to impair movement, especially on heterogeneous or uneven substrates. To evaluate this prediction, we examined locomotor behavior in the land hermit crab Coenobita compressus on Coiba Island (Panama), integrating field observations with controlled experimental assays across substrates differing in topography and compaction. Contrary to classical expectations, shell weight and morphology exerted limited effects on locomotor performance. Instead, individuals exhibited substantial behavioral flexibility, adjusting posture and gait across environmental contexts. These findings suggest that C. compressus may buffer mechanical constraints imposed by shell architecture through adaptive behavioral compensation. Our results support an expanded interpretation of the trade-off framework in which behavioral plasticity attenuates, rather than eliminates, functional trade-offs, potentially enhancing performance in dynamic coastal habitats.
Animal personality is a concept in behavioural ecology that describes consistent inter-individual variation in behavior. These behavioral tendencies are stable across different contexts and throughout an individual's life. Increasing evidence shows that variation in individual personality of animals is related to variation in their cognitive ability (e.g. spatial learning), but the findings on such links are contradictory among and even within species. This study examined how personality traits (boldness and activity) relate to spatial learning in crucian carp (Carassius auratus), specifically to determine their reliance on allocentric (landmark-based) navigation. Fish were trained under two conditions: a visual landmark absent and present. As trials progressed, latency to complete the foraging task and theG number of fish turn-backs decreased in both treatments. However, the percentage of correct choices increased significantly only in the landmark present condition, with no marked improvement in the landmark absent condition. This indicates that the presence of a landmark enhanced learning efficiency, suggesting a reliance on allocentric navigation. Despite this, neither boldness nor activity predicted individual learning performance in landmark present context. Our findings demonstrate that environmental structure, specifically the presence of landmarks, is a critical factor in spatial learning for crucian carp, but the personality traits measured here do not underpin individual variation in this cognitive ability within the tested contexts.
