Andrew Ryan’s research while affiliated with University College Dublin and other places

Human-wildlife conflict in expanding peri-urban and urban areas is of increasing concern, as a result of growing human populations along with the associated anthropogenic footprint on wildlife habitats. Empirical data from wildlife research carried out within human dominated landscapes are key to understanding the effects of human pressures on wildlife ecology and behaviour, exploring wildlife behavioural flexibility (or phenotypic plasticity), and informing wildlife management decisions. Here, we explored how female fallow deer (Dama dama) responded to human and dog presence during the birthing period in the largest walled urban park in Europe. We collected data on 477 bedsites utilised by 283 neonate fawns across three consecutive fawning seasons, gathered fine-scale data on humans and dogs space use, and built Resource Selection Functions at multiple spatial scales. We found that, when choosing bedsites to give birth and leave fawns unattended, fallow deer mothers significantly avoided hotspots of park visitors on foot (and their dogs) along the hiking trail routes. Bedsites were also unlikely to be in close proximity of paved roads used by vehicle traffic. Additionally, fallow deer mothers were found to select for dense understory vegetation for bedsites, providing low visibility to conceal their offspring. Our results provide detailed insights into bedsite spatial and habitat selection by a large herbivore in response to human activities, and we provide clear indications to wildlife managers to preserve established fawning sites and alleviate human-wildlife conflict during a critical period of the deer annual biological cycle.

Toxoplasma gondii ( T. gondii ) is a trophically-transmitted protozoan parasite that has been suggested to facilitate its transmission by altering intermediate hosts’ anti-predator behaviour, thus increasing the likelihood of completing the cycle inside its definitive host i.e. domestic and wild felines. T. gondii has been linked to reduced risk-aversion, slower reaction times, and more exploratory behaviours in intermediate hosts, including most famously weakened aversion to the scent of feline predators in mice. Studies examining this phenomenon, however, have almost exclusively been carried out in laboratory conditions with small mammals, whereas little is known about the role of T. gondii within more complex ecological contexts involving large mammals in the wild. Under such scenario, the goals of our study were three-fold. Firstly, to determine the prevalence of T. gondii infection in a population of free-living fallow deer ( Dama dama ) living in a park at the edge of a metropolis. Secondly, to find a link between deer seropositivity and space use in the park, namely proximity to buildings with domestic cats, where deer may have been more likely to contract the disease. Finally, to determine whether infection with T. gondii was linked to risk taking behaviour in these free ranging large mammals, namely likelihood to approach park visitors. To achieve our goals, we estimated seropositivity and combined it with spatial distribution and behavioural data of individually-recognizable deer ranging from those that avoid humans (risk-avoiders) to those who beg for food (risk-takers). We found T. gondii to be quite widespread in this population with a seropositive of 20% (24 out of 120 individuals). Contrary to our expectations, we found no correlation between T. gondii seropositivity and space use in the park, therefore not allowing us to engage with the dynamics of disease contraction. We did however find that fallow deer taking the risk of approaching humans were also more likely to be seropositive. Are risk taking individuals more likely to contract the disease? Or, alternatively, do they take more risk because they have contracted the disease? The causal mechanism behind our result has yet to be disentangled, opening new scenarios in research aimed at tackling host manipulation in this parasite. It is a fact, however, that those animals that were more likely to be in contact with the public were also those more likely to be seropositive, adding key empirical evidence to the study of zoonotic diseases. Our study is a significant contribution on the transmission and maintenance dynamics of T. gondii , offering new insights on the need to conduct longitudinal studies able to disentangle the causal mechanism and T. gondii ’s ability to manipulate its intermediate host.

SARS-CoV-2 can infect wildlife, and SARS-CoV-2 variants of concern might expand into novel animal reservoirs, potentially by reverse zoonosis. White-tailed deer and mule deer of North America are the only deer species in which SARS-CoV-2 has been documented, raising the question of whether other reservoir species exist. We report cases of SARS-CoV-2 seropositivity in a fallow deer population located in Dublin, Ireland. Sampled deer were seronegative in 2020 when the Alpha variant was circulating in humans, 1 deer was seropositive for the Delta variant in 2021, and 12/21 (57%) sampled deer were seropositive for the Omicron variant in 2022, suggesting host tropism expansion as new variants emerged in humans. Omicron BA.1 was capable of infecting fallow deer lung type-2 pneumocytes and type-1–like pneumocytes or endothelial cells ex vivo. Ongoing surveillance to identify novel SARS-CoV-2 reservoirs is needed to prevent public health risks during human–animal interactions in periurban settings.

Human populations continue to grow at an unprecedented pace, alongside the anthropogenic footprint on wildlife habitats. As a result, human-wildlife conflict in expanding peri-urban and urban areas is of increasing concern. Empirical data from wildlife research carried out within human dominated landscapes are key to understanding the effects of human pressures on wildlife ecology and behaviour, appreciate wildlife behavioural flexibility (or phenotypic plasticity), and inform wildlife management decisions. Here, we studied how female fallow deer (Dama dama) and their fawns adapted their behaviour during the birthing period in the largest urban park of Europe, which receives 10 million visitors along with their dogs every year. We collected data on 481 bedsites utilised by 285 neonate fawns across three consecutive fawning seasons, gathered fine-scale data on humans (and dogs) access, and built Resource Selection Functions at multiple spatial scales. We found that, when choosing the bedsites to give birth and leave fawns unattended, fallow deer mothers significantly avoided hotspots of park visitors on foot (and their dogs) along the hiking trail network, maintaining a distance of at least ~200m. Bedsites were unlikely to be in close proximity, within 50 meters, of paved roads used by vehicle traffic. Fallow deer mothers also were found to select for dense understory vegetation for their fawns bedsites, providing low visibility to conceal them. Our results give a very detailed overview of the behavioural adaptations of fallow deer mothers during fawning, and provide clear indications to wildlife managers to preserve traditional fawning sites and alleviate human-wildlife conflict during a critical period of the deer annual biological cycle.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infects wildlife. Recent studies highlighted that variants of concern (VOC) may expand into novel animal reservoirs with the potential for reverse zoonosis. North American white-tailed deer are the only deer species in which SARS-CoV-2 has been documented, raising the question whether further reservoir species exist as new VOC emerge. Here, we report the first cases of deer SARS-CoV-2 seropositivity in Eurasia, in a city population of fallow deer in Dublin, Ireland. Deer were seronegative in 2020 (circulating variant in humans: Alpha), one animal was seropositive in 2021 (Delta variant), and 57% of animals tested in 2022 were seropositive (Omicron variant). Ex vivo, a clinical isolate of Omicron BA.1 infected fallow deer precision cut lung slice type-2 pneumocytes, also a major target of infection in human lungs. Our findings suggest a change in host tropism as new variants emerged in the human reservoir, highlighting the importance of continued wildlife disease monitoring and limiting human-wildlife contacts. Teaser: This study is the first report of SARS-CoV-2 seropositivity in fallow deer, highlighting expansion of viral variants into new host reservoirs.

Although it is widely acknowledged that animal personality plays a key role in ecology, current debate focuses on the exact role of personality in mediating life-history trade-offs. Crucial for our understanding is the relationship between personality and resource acquisition, which is poorly understood, especially during early stages of development. Here we studied how among-individual differences in behavior develop over the frst 6 months of life, and their potential association with resource acquisition in a free-ranging population of fallow deer (Dama dama). We related neonate physiological (heart rate) and behavioral (latency to leave at release) anti-predator responses to human handling to the proportion of time fawns spent scanning during their frst summer and autumn of life. We then investigated whether there was a trade-off between scanning time and foraging time in these juveniles, and how it developed over their frst 6 months of life. We found that neonates with longer latencies at capture (i.e., risk-takers) spent less time scanning their environment, but that this relationship was only present when fawns were 3–6 months old during autumn, and not when fawns were only 1–2 months old during summer. We also found that time spent scanning was negatively related to time spent foraging and that this relationship became stronger over time, as fawns gradually switch from a nutrition rich (milk) to a nutrition poor (grass) diet. Our results highlight a potential mechanistic pathway in which neonate personality may drive differences in early-life resource acquisition of a large social mammal.

Current debate in the field of animal personality revolves around whether personality is reflecting individual differences in resource allocation or acquisition. Despite the large body of literature, the proximate relationships between personality, resource allocation, and acquisition are still unclear, especially during early stages of development. Here we studied how among-individual differences in behaviour develop over the first 6 months of life, and their potential association with resource acquisition in a free-ranging population of fallow deer (Dama dama). We related proxies of neonate personality, i.e. neonate physiological (heart rate) and behavioural (latency to leave at release) anti-predator responses to human handling, to the proportion of time fawns allocated to scanning during their first summer and autumn of life. We then investigated whether there was a trade-off between scanning time and foraging time in these juveniles, and how it developed over their first 6 months of life. We found that neonates with longer latencies at capture (i.e. risk-takers) allocated less time scanning their environment, but that this relationship was only present when fawns were 3-6 months old during autumn, but not when fawns were only 1-2 months old during summer. We also found that time spent scanning was negatively related to time spent foraging, a relationship rarely tested in juveniles of large mammals, and that this relationship becomes stronger over time, as fawns gradually switch from a nutrition rich (milk) to a nutrition poor (grass) diet. Our results highlight a potential mechanistic pathway in which neonate personality may drive differences in early-life resource acquisition, through allocation, of a large social mammal.