Social ecology of wildlife disease
Encounters between individuals comprise the webs of interactions through which social animals transmit information and provide material support. They also serve as conduits of infection. While social interactions (and the diseases they parasites and pathogens) are generally considered from the perspective of individual host species, multi-host pathogens (those capable of infecting multiple species; think bird flu, Ebola virus disease, and COVID-19) travel along expanded networks including additional connections between individuals of different species.
For my master’s research I studied how social interactions—both within and between species—relate to the probability of being infected by multi-host parasites. This work was carried out at Brookfield Conservation Park with collaborators Allison Johnson and Laura Vander Meiden. Brookfield is home to slightly uphill of 100 species of birds that collectively demonstrate a strikingly diverse spectrum of social behaviors. From solitary, wandering malleefowl (Leipoa ocellata) to massive hordes of chestnut-crowned babblers (Pomatostomus ruficeps) and mixed-species flocks of fairy-wrens (Malurus spp.), thornbills (Acanthiza spp.), weebills (Smicrornis brevirostris), red-capped robins (Petroica goodenovii) and more, Brookfield’s birds made for a great system in which to study the effects of nuanced differences in social behavior between species. I hypothesized that more social birds—those making frequent interactions with other conspecific and heterospecific individuals—would be at a greater risk of infection. If this is the case, then at the species level we would expect to see species that are comparatively social having a higher prevalence (proportion of infected individuals in the population).
We captured collected small blood samples from 889 individuals of 23 different species, which we then tested for haemosporidian blood parasite infection. Transmitted between individuals by mosquitoes and other insect vectors, haemosporidians can cause disease similar to malaria in birds, and have been identified as a key factor in the decline of some of Hawai’i’s native avifauna. Most species that we tested appeared to be free of infection. Among the species that did have infections, we found substantial variation in the prevalence of blood parasite infections.
During the same period, we (mostly Laura!) spent hours watching mixed-species foraging flocks, making note of the numbers of individuals of each species involved, their foraging height, and other details. From these observations, we constructed a foraging network model of the avian community at Brookfield, using the frequency and intensity (as measured by the number of individuals of each species present during each encounter) of co-occurrences in foraging flocks as an index of association. From this network we were able to infer which species might be at highest risk of infection, if the hypothesis (that social interactions in the form of flocking behavior increase the risk of acquiring infection) was true.
Other projects
Numenon is a little \(\texttt{shiny}\) app illustrating an acoustic geography of North American birds. It’s based on a description of the thick-billed parrot (Rhynchopsitta pachyrhyncha) as the “numenon of the Sierra Madre” by Aldo Leopold in 1937. This concept was expanded and developed by Ethan Linck and Ben Freeman to describe the essential soundscape of the North American avifauna entire.
Social ecology of wildlife disease
Encounters between individuals comprise the webs of interactions through which social animals transmit information and provide material support. They also serve as conduits of infection. While social interactions (and the diseases they parasites and pathogens) are generally considered from the perspective of individual host species, multi-host pathogens (those capable of infecting multiple species; think bird flu, Ebola virus disease, and COVID-19) travel along expanded networks including additional connections between individuals of different species.
Figure 1: Mallee woodlands of Brookfield under the dull sienna sky of a late-spring dust storm.
For my master’s research I studied how social interactions—both within and between species—relate to the probability of being infected by multi-host parasites. This work was carried out at Brookfield Conservation Park with collaborators Allison Johnson and Laura Vander Meiden. Brookfield is home to slightly uphill of 100 species of birds that collectively demonstrate a strikingly diverse spectrum of social behaviors. From solitary, wandering malleefowl (Leipoa ocellata) to massive hordes of chestnut-crowned babblers (Pomatostomus ruficeps) and mixed-species flocks of fairy-wrens (Malurus spp.), thornbills (Acanthiza spp.), weebills (Smicrornis brevirostris), red-capped robins (Petroica goodenovii) and more, Brookfield’s birds made for a great system in which to study the effects of nuanced differences in social behavior between species. I hypothesized that more social birds—those making frequent interactions with other conspecific and heterospecific individuals—would be at a greater risk of infection. If this is the case, then at the species level we would expect to see species that are comparatively social having a higher prevalence (proportion of infected individuals in the population).
We captured collected small blood samples from 889 individuals of 23 different species, which we then tested for haemosporidian blood parasite infection. Transmitted between individuals by mosquitoes and other insect vectors, haemosporidians can cause disease similar to malaria in birds, and have been identified as a key factor in the decline of some of Hawai’i’s native avifauna. Most species that we tested appeared to be free of infection. Among the species that did have infections, we found substantial variation in the prevalence of blood parasite infections.
Figure 2: Prevalence of haemosporidian infections among 8 bird species at Brookfield Conservation Park.
During the same period, we (mostly Laura!) spent hours watching mixed-species foraging flocks, making note of the numbers of individuals of each species involved, their foraging height, and other details. From these observations, we constructed a foraging network model of the avian community at Brookfield, using the frequency and intensity (as measured by the number of individuals of each species present during each encounter) of co-occurrences in foraging flocks as an index of association. From this network we were able to infer which species might be at highest risk of infection, if the hypothesis (that social interactions in the form of flocking behavior increase the risk of acquiring infection) was true.
Figure 3: Mixed-species flocking network