Biology subjects

Daversa, D. R.

Publications and source records attributed to Daversa, D. R..

6 recordsLinked to original sources

bioRxiv2026

Can urban fence lizards identify cats?

Urban habitats can serve as wildlife refuges, or as ecological traps. As global urbanization continues to increase, native prey species may experience reduced threat from natural predators that tend to avoid human-populated areas. However, such protection often comes at the expense of susceptibility to synanthropic predators, one of the most prevalent being domestic house cats (Felis catus). While cats are a known driving force of mortalities in urban wildlife, their sublethal effects remain understudied. To better understand the behavioral effects of synanthropic predators on native urban prey, we examined responses of western fence lizards (Sceloporus occidentalis) to Artificial Intelligence (AI)-generated visual stimuli of native predators (snakes) and synanthropic predators (house cats). Visual stimuli included: California striped racers (Masticophis lateralis), a native predator; domestic cats, a synanthropic mammalian predator (Felis catus); and desert cottontails (Sylvilagus audubonii), a native mammalian non-predator. We quantified lizard responses as the change in rates of looking and locomotion during and following the video presentation. Our results revealed that lizards discriminated cats from the control by looking more within the first 90 seconds following exposure. Lizards looked more across the entire 5-minute observation period following exposure to all stimulus types compared to control conditions, indicating that AI generated visual stimuli effectively elicit behavioral responses. Together, these findings indicate that urban lizards initially detect and respond to visual cues of cats, suggesting that cat-induced mortality is not a result of inability to detect such predators. Thus, cats influence urban prey not only through direct predation risk, but also changes in behavior associated with the presence of synanthropic predators.

ecology↗

bioRxiv2025

Chytrid fungal infections in alpine toads proliferate during winter dormancy

The spread and impact of wildlife pathogens is often seasonal, and identifying the seasons of high impact is critical to biodiversity and public health management. Here, we report new evidence that winter host dormancy, a period generally neglected in terms of pathogen seasonal dynamics, promotes the spread of infection from the globally threatening amphibian fungal pathogen, Batrachochytrium dendrobatidis (Bd). Bd surveillance of Yosemite toads (Anaxyrus canorus) during their first year of life showed that: (a) detectable Bd infections were nearly absent in the tadpole stage and immediately after metamorphosis, (b) Bd prevalence and intensity gradually increased during the first two months of post-metamorphic growth, and (c) Bd prevalence and intensity increased four-fold in toads during the first winter dormancy. High prevalence and intensity of Bd infections after winter dormancy was observed in yearling toads across two consecutive years and was much higher than that observed in aquatically breeding adults during the same timeframe. To our knowledge, this is the first evidence from wild amphibians that Bd proliferates during terrestrial winter dormancy. This discovery calls for a reconsideration of the seasons enabling the proliferation and persistence of Bd and identifies recently metamorphosed hosts as overwinter Bd reservoirs. More generally, the study underscores the importance of host dormancy in pathogen persistence and seasonal infection spread.

ecology↗

bioRxiv2025

Host species composition, not priority effects, determines infection risk in multihost-multiparasite amphibian communities

Novel parasite emergences are posing uncertain threats to wildlife communities worldwide. Because parasites typically infect multiple host species and interact with other parasites, the degree of threat posed by these emergences is known to depend both on a communitys host species composition and history of exposure to other parasites. What is not known is how these two factors - multi-host effects and multi-parasite effects - interact to shape the outcomes of parasite emergences. We experimentally investigated the outcomes of sequential emergences by two amphibian parasites of major concern to global biodiversity, Batrachochytrium dendrobatidis (Bd) and Ranavirus (Rv). Mimicking sequential Bd and Rv emergence in communities comprising either larval common toads (Bufo bufo), larval common frogs (Rana temporaria), or both host species, showed that host community composition influenced subsequent patterns of Bd and Rv infection much more than the presence of the other parasite. Bd prevalence varied predictably with host community composition; toads exhibited consistently higher Bd infection probabilities than frogs across all scenarios. Variation in community-level prevalence therefore was explained by differences in the relative abundance of toads. In contrast, community-level Rv prevalence was not consistently driven by a single host species. Going from single-host to two-host communities reversed relative Rv infection probabilities in frogs versus toads; when kept separately, frogs had a higher Rv infection probability than toads, but toads had a higher infection probability than frogs when the two species were co-housed. Host species composition can therefore alter multi-parasite infection dynamics not only through changes in the abundance of primary host species, but also through changes in which species appear to act as the primary hosts. These insights suggest that Bd-Rv dynamics in single-host scenarios may not reflect those occurring in natural multihost communities, and the observed context-dependency in the apparent primary host species for Rv highlights an overlooked factor potentially shaping biodiversity-disease relationships.

ecology↗

bioRxiv2023

Standard methods for marking caudate amphibians do not impair animal welfare over the short term: an experimental approach

Major advancements in ecology and biodiversity conservation have been made thanks to methods for marking and individually tracking animals. Marking animals is both widely used and controversial due to the potential consequences to animal welfare, which are often incompletely evaluated before implementation. Two outstanding knowledge gaps concerning the welfare consequences of individual marking concerns their short-term behavioural impacts and the relative impacts from marking versus the handling of animals while carrying out procedures. We addressed these knowledge gaps through an experimental study of alpine newts (Ichthyosaura alpestris) in which we varied handling and marking procedures. Examining individual responses to handling, toe-clipping and visible implant elastomer (VIE) injection over 21 days showed that handling and marking elicited increased newt activity and hesitancy to feed compared to animals that did not get handled or marked. These effects were apparent even when animals were handled only (not marked), and marking did not further increase the magnitude of responses. Increases in newt activity and feeding hesitancy were transient; they were not observed in the weeks following handling and marking. Whereas previous studies emphasize the welfare impacts of marking procedures themselves, these findings highlight that handling alone can elicit behavioural changes with possible costs to welfare. Yet, the transient nature of behavioural responses observed here suggests that immediate costs of handling may be subsequently compensated for.

animal behavior and cognition↗

bioRxiv2020

Habitat patchiness drives spatial structure in morphological trait variation and co-variation in spotted salamanders (Ambystoma maculatum)

The influence of intraspecific trait variation on species interactions makes trait-based approaches critical to understanding eco-evolutionary processes. Because species occupy habitats that are patchily distributed in space, advancement in trait-based ecology hinges on understanding how trait variation is distributed within and between habitat patches. We sampled larval spotted salamanders (Ambystoma maculatum) across spatially discrete ponds to quantify within- and between-pond variation in mass, length, and their allometric relationship. Between-pond variation explained 7-35% of total observed variation in the length and shape of salamander larvae, depending on the body segment measured (i.e., head, body, or tail). Salamander tail morphology was more variable and exhibited more between-pond variation than head or body morphology. Salamander mass was highly variable and strongly correlated with total length. Allometric analysis revealed that the slopes of mass-length relationships were similar across ponds, but that intercepts differed across ponds. Preliminary evidence hinted that newly constructed ponds were a driver of the observed differences in mass-length relationships. Pond construction may therefore bolster trait diversity across the broader landscape, and in so doing instil more adaptive potential of salamander populations under current and future environmental change.

ecology↗

bioRxiv2019

Beyond the ecology of fear: non-lethal effects of predators are strong whereas those of parasites are diverse

The ecology of fear demonstrates how prey responses to avoid predation cause non-lethal effects at all ecological scales. Parasites also elicit defensive responses in hosts with associated non-lethal effects, which raises the longstanding, yet unresolved question of how non-lethal effects of parasites compare with those of predators. We developed a framework for systematically answering this question for all types of predator and parasite systems. Our framework predicts that trait responses and their non-lethal effects should be strongest from predators and parasites that do not kill individuals to feed on them, but which nevertheless damage fitness. Analysing trait response data on amphibians, which have been well-studied for this area of research, showed that individuals generally responded more directly to short-term predation risks than to parasitism. Apart from studies using amphibians, there have been few direct comparisons of responses to predation and parasitism, and none have incorporated responses to micropredators, parasitoids, or parasitic castrators, or examined their long-term consequences. Addressing these and other data gaps highlighted by our general framework can advance the field toward understanding how non-lethal effects shape real food webs, which contain multiple predator and parasite species.

ecology↗