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Present and past projects

Small mammal communities in urban habitats

Together with Melanie Dammhahn (University of Münster) and several students, I am investigating which characteristics of the urban matrix predict changes in the small mammal community in Münster and surroundings.

Health of urban gray squirrles

Together with collaborators Herman Pontzer (Duke University), Olivia Petritz and Julie Balko (vets at NC State University), I am investigating whether Eastern gray squirrels (Sciurus carolinensis) from urban and rural environments differ in body mass and health parameters such as blood lipids, glucose, liver values, hematology and blood biochemistry (manuscript in revision at Urban Ecosystems).

Comfortably numb? Does urbanization change grey squirrel stress levels?

Together with Herman Pontzer, Alannah Grant, Mason Stothart, Pratik Gupte and Amy Newman, I investigated how cortisol levels of Eastern gray squirrels (Sciurus carolinensis) change when the level of urbanization increases. We measured cortisol levels in hair samples from squirrels in the USA and Canada and found that squirrels have lower hair cortisol levels in the most urbanized habitats in Canada, but not in the samples from the USA. This research is published in the Urban Naturalist.

Trash bin usage by squirrels -when do they feed on trash and what is it they eat?

Together with Herman Pontzer, Gabrielle Butler, Claire Parker, Pratik Gupte and Jörg Jäger, we observed trash bins on Duke University campus and  examined which environmental factors influence if squirrels use trash bins to forage. We also studied which kind of food items they retrieved from the bins and how their usage of the bins varied between seasons. This research is published in Mammalian Biology.


Does an increase in physical activity result in better cardiometabolic health?

Together with Herman Pontzer (Duke University), I investigated physical activity and metabolic markers in ring‐ tailed lemurs (Lemur catta) and Coquerel's sifakas (Propithecus coquereli) at Duke Lemur Center during a period of low activity in winter and a period of high activity in large free‐ranging outdoor enclosures. We compared body mass, blood glucose, triglycerides, HDL‐ and LDL‐cholesterol, physical activity via accelerometry, and total energy expenditure (TEE) via the doubly labeled water method (in ring‐tailed lemurs only) between both conditions. Both species were more active and had a lower body mass in summer. Individuals that increased their activity more, also lost more body mass. Changes in activity were not associated with changes in markers of metabolic health, body fat percentage and TEE (both unadjusted and adjusted for body composition). This research is published in American Journal of Primatology.

How does a small rodent adjust to a harsh dry season?

Together with collaborators Carsten Schradin (CNRS, France) and Neville Pillay (Wits, South Africa), I combined measurements of resting metabolic rate, daily energy expenditure (using the doubly labeled water method) and behavioral observations to understand how African striped mice (Rhabdomys pumilio) regulate their energy expenditure via physiological and/or behavioral adjustments. We also examined which environmental factor - ambient temperature or food availability - is the main driver of seasonal changes in their resting metabolic rate. Male striped mice follow alternative reproductive tactics. We examined behavioral differences and differences in energy expenditure between males following different tactics and found that solitary roamers spend more energy than group-living males. Check out the Publications section to find out more about these studies.

PhD research "Effects of fragmentation on brown spider monkeys (Ateles hybridus) and red howler monkeys (Alouatta seniculus)"

I combined behavioral observations with data on fecal glucocorticoid metabolite (FGCM) levels to investigated the endocrine and behavioral responses of primates to anthropogenic disturbances in Colombia. In a first step, validated an enzymeimmunoassay (EIA) for the analyses of FGCM levels of both species. While forest fragment size did not influence FGCM levels in either species, spider monkeys, but not howler monkeys, showed elevated FGCMs in fragments with the highest level of human impact. These results suggest that the two species differ in their physiological responsiveness to anthropogenic changes, further emphasizing why brown spider monkeys are at higher extinction risk than red howler monkeys. Spider monkeys exhibit flexible grouping patterns (fission-fusion dynamics) and adjust subgroup size to food availability. When studied in a small forest fragment (65 ha), they showed an atypical grouping pattern with smaller subgroups (and also higher FGCM levels and higher aggression rates) when fruit availability was high compared to when it was low.


Together with collaborators Donal Bisanzio, Nelson Galvis, Andres Link, Anthony Di Fiore and Thomas Gillespie, I showed that physical contact affects the spread of gastrointestinal parasites in spider monkeys, supporting the idea that pathogen transmission is a cost associated with sociality.

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