Biology subjects

Rozen-Rechels, D.

Publications and source records attributed to Rozen-Rechels, D..

4 recordsLinked to original sources

bioRxiv2025

Group size influences behavioral plasticity in responses to thermoregulation-foraging trade-offs by a socially cohesive bird

Behavioral plasticity, such as changes in habitat use and activity, can be a critical modulator of thermal pressures on endotherms. However, shifts in behaviors can meet diversified costs such as missed feeding opportunities. Individual decision-making should therefore capture the trade-off between the costs and the benefits of thermoregulation. In the case of social species, the decision process could also be facilitated or slowed down by the modulation of costs arising through the social environment. In this study, we tested how vulturine guineafowl (Acryllium vulturinum) change their use of open areas (where they predominately forage) according to heat using GPS data from 105 birds collected every 5 minutes for 6 months. Because animals vary in their sensitivity to risk according to group size--e.g. due to the dilution effect--we compared the responses of individuals depending on the size of the group they belong to. We also analyzed if behavioral responses translate into less precise thermoregulation by recording the body temperature of a subset of birds in two groups. We foundd that birds avoid heat by selectively using open areas and moving to cover, as well as reducing activity when temperature increases, birds use open areas less and move less. Individuals from intermediate-sized groups seemed to be able to use open areas during warmer conditions compared to individuals from small and large groups (10% higher probability of use). However, active birds in the open did not present hyperthermia, suggesting that behavioral changes are efficient or that individuals have other efficient strategies such as physiological cooling. Together, these results indicated that responses to high temperatures are complex, as they included not only a range of environmental constraints but that responses can also vary according to social context.

ecology↗

bioRxiv2025

Lead exposure positively affects coccidia abundance in feral pigeons (Columba livia)

O_LIIn urban environments, organisms are exposed to high levels of pollutants, including trace metals, whose concentrations can be increased by anthropogenic activities. Numerous studies have shown the toxic effects of pollutants on exposed organisms. However, due to their life within the host, parasites can also be affected by exposure to these pollutants. Overall, previous correlative findings reveal that the effects of parasite exposure to pollutants through the host can vary, from positive to negative, highlighting the complexity of host-parasite-environment interactions in relation to pollution. C_LIO_LIIn this study, we experimentally tested whether lead exposure affects the abundance of ecto-, meso-, and endoparasites in wild pigeons (Columba livia), which host a wide variety of parasites and are naturally exposed to trace metals in urban environments. As we had previously reported the toxic effects of lead on the immune system of pigeons, we expected lead exposure to be indirectly beneficial for the parasites. C_LIO_LITo test this, we used a sample of wild pigeons captured in Paris, half of which were experimentally exposed to lead concentrations similar to those found in Paris. We then measured the abundance of several parasites: blood parasites (hemosporidian parasites), ectoparasites (Columbicola columbae and Campanulote compar), coccidia and helminths. Additionally, we measured the intensity of the pigeons antiparasitic behavioral response (grooming) through behavioral analyses. C_LIO_LIOur results did not reveal toxic effects of lead exposure on the parasites. On the contrary, we found positive effects of this exposure on coccidia abundance in male pigeons. This result could be explained by a toxic effect of lead on the hosts antiparasitic immune strategy, making the hosts less hostile to parasites. However, we found no effect of lead exposure on the abundance of lice, blood parasites and helminths. This could be explained by the lack of impact of lead exposure on grooming antiparasitic activity in our experiment, and by seasonal variations in the activity of blood parasite vectors, which may have masked potential effects of our treatment. C_LIO_LIIn conclusion, our study highlights the importance of considering the host environment, particularly pollutants, to understand parasite dynamics. C_LI

ecology↗

bioRxiv2025

Interactions between parasites within the host: helminth infection reduces lice abundance in feral pigeons (Columba livia)

O_LIWithin a host, parasites form a community and interact with each another. They can interact directly through competition for space or indirectly through competition for resources, or even via the hosts immune response. These interactions can influence infection patterns within the host. In particular, helminths are capable of facilitating the infection of other parasites through their immunosuppressive effects or hindering it by activating immune responses that reduce the ability of other species to infest the host. C_LIO_LIIn this study, we aimed to test the existence of parasite interactions in the wild pigeon host (Columba livia). More specifically, we experimentally tested whether helminth infestation influences the infestation dynamics of ecto- and endoparasites in pigeons. C_LIO_LIOur predictions were tested on a sample of pigeons captured in Paris, half of them were exposed to an anthelmintic treatment. We then assessed the effects of this deworming treatment on the abundance of blood parasites (hemosporidian parasites, Haemoproteus spp., Plasmodium spp., and Leucocytozoon spp.), lice (Columbicola columbae and Campanulote compar), as well as on the intensity of antiparasitic behavioral responses (preening). C_LIO_LIWe detected a negative relationship between helminth presence and lice abundance, with higher lice abundance when helminths were reduced (with anthelmintic treatment) and lower lice abundance when helminths were more abundant (without anthelmintic treatment), indicating inhibitory effects of helminths on ectoparasite abundance. However, these results were not supported by differences in preening activity between the two experimental groups, suggesting that other mechanisms are involved. Our results showed no effect of anthelmintic treatment on the abundance of blood parasites. The mechanism by which helminths induced ectoparasite repulsion remains to be demonstrated. C_LIO_LIOur study highlights the importance of considering interactions between different types of parasites in an eco-epidemiological approach when taking into account the factors affecting parasite prevalence and abundance. C_LI

ecology↗

bioRxiv2023

Habitat structural complexity increases age-class coexistence and productivity in fish populations

Structurally-complex habitats harbour more taxonomically-diverse and more productive communities, a phenomenon generally ascribed to habitat complexity relaxing the strength of inter-specific predation and competition. Here, we extend this classical, community-centred view by showing that positive complexity-diversity and complexity-productivity relationships may also emerge from between-age-class, intra-specific interactions at a single-population level. In the laboratory, we show that medaka fish (Oryzias latipes) are strongly cannibalistic in complexity-free habitats, and that cannibalism may occur over a wide range of victim/cannibal body size ratios. In replicated outdoor pond populations, we manipulated habitat structural complexity using floating artificial structures, which selectively hampered movements of large-bodied medaka. Habitat complexity relaxed the strength of cannibalism, resulting in (1) increased survival of age-0+ individuals, (2) elevated age-class diversity, (3) increased population growth rate, and (4) dampened negative density-dependence in the stock-recruitment relationship reflecting elevated habitat carrying capacity. The resultant higher population density in complex habitats was associated with increased competition for food among both age-0+ and age-1+ individuals. Our results highlight that positive complexity-diversity and complexity-productivity relationships may be considered as a generally-emergent property of size-structured populations and communities in which a larger body size brings a predation or interference advantage. Hence, enhancement of habitat structural complexity may be seen as a pivotal management strategy not only in favour of taxonomic diversity, but also to increase the productivity and resilience of exploited populations and to improve the conservation status of endangered species.

ecology↗