Date of Degree

6-2022

Document Type

Dissertation

Degree Name

Ph.D.

Program

Anthropology

Advisor

Jessica M. Rothman

Committee Members

Larissa Swedell

Andrea L. Baden

Patricia Wright

Subject Categories

Behavior and Ethology | Biological and Physical Anthropology | Other Ecology and Evolutionary Biology | Other Nutrition

Keywords

Lemur, Nutritional Ecology, Madagascar, Primates, Niche

Abstract

Animals must navigate complex food and nutrient environments that are constantly in flux to obtain the macro and micronutrients necessary for their growth, reproduction, and survival. The nutritional needs of animals also vary over the life course, further complicating the search for adequate foods and the nutrients within them. The hypervariable and unpredictable environment of Madagascar creates a complex nutrient landscape for lemurs in particular because they are subject to large fluctuations in food availability. These fluctuations are thought to create extreme periods of nutritional stress during the dry season (known as the lean season) for lemurs. In response, lemurs are posited to have evolved a suite of traits that allow them to cope with their harsh environment.

Using the tools of nutritional ecology, the relationship between the lean season and the macronutrient intakes and balances of three species of lemurs, the Milne-Edwards sifaka (Propithecus edwardsi), the Verreaux’s sifaka (Propithecus verreauxi), and the red-fronted brown lemur (Eulemur rufifrons) were examined. One hundred and nineteen full-day focal follows of adult individuals from two groups of each of the three study species (P. edwardsi: N = 31; E. rufifrons: N = 25; P. verreauxi: N = 63) were conducted in two habitats, Ranomafana National Park and Kirindy Mitea National Park, Madagascar. Food samples (N=270) were collected and analyzed for macronutrient contents using wet chemistry analyses. The degree of dietary and nutritional specialization shown by each species was investigated. Additionally, the nutritional niches of the study species were modeled, and the utility of the nutritional niche to examine niche overlap between the species was tested.

First the diets and nutrient strategies of the study species were characterized in relation to the lean season. E. rufifrons and P. verreauxi were both found to be dietary specialists with E. rufifrons mainly consuming ripe fruits and P. verreauxi focusing on mature leaves. P. edwardsi were the most generalist feeders. The study species were found to have dry matter and macronutrient intakes below those found for other lemur and non-lemur primates. Energetically, all species appeared to ingest the minimum amount necessary for a lemur. P. edwardsi, however, appeared to be protein deficient. The diets of P. verreauxi and P. edwardsi both shifted between the early dry and late dry season, but the nutrient intakes of both species remained largely the same. Only the intake of available protein was found to significantly change; P. verreauxi increased their intake and P. edwardsi decreased their intake. Overall, each species appeared to have been able to achieve similar nutrient and energy intakes to other lemur species and to the minimum amount outlined by the National Resource Council (NRC 2003).

Second, the daily macronutrient balances, potential rules of compromised utilized, and sex-specific differences were examined. The species were found to target specific balances of non-protein energy to available protein (NPE:AP). The NPE:AP balances for P. edwardsi and E. rufifrons were higher than the balance found for P. verreauxi. Females of each species were also found to consistently target higher NPE:AP balance than the males. P. edwardsi and E. rufifrons prioritized the intake of AP rather than NPE. P. verreauxi instead prioritized the intake of NPE. The protein prioritization seen in P. edwardsi and E. rufifrons may be a consequence of the low protein concentrations in the fruits of Madagascar and suggests that protein is a limiting nutrient.

Third, the nutritional niches of the three study species were modeled and their utility for examining the degree of specialization shown by each species was tested. Finally, niche overlap between each species was then quantified along the nutrient dimensions. P. verreauxi had the most restricted niches of the species. P. edwardsi and E. rufifrons had much broader niches. The nutrient niche of P. verreauxi suggests that they are more restricted in their nutrient landscape both in terms of the food compositions available to them and the foods that they selectively consumed. Density heatmap peaks showed the distribution of the daily macronutrient balances and found the niches of P. edwardsi and E. rufifrons to be more restricted than previously estimated suggesting macronutrient intake specialism. P. verreauxi appeared to be food composition specialists and macronutrient intake specialists while P. edwardsi and E. rufifrons are food composition generalists and macronutrient intake specialists. Niche overlap between the species was quantified, and the greatest overlap was found between P. edwardsi and E. rufifrons. The overlap between P. edwardsi and E. rufifrons suggests that the species potentially compete over resources, but the larger niche quantified for E. rufifrons suggests that E. rufifrons may be able to utilize a different set of resources to avoid direct competition with P. edwardsi.

Overall, all lemurs studied were found to consume relatively small amounts of dry matter and low amounts of energy and macronutrients in the lean season. The data generated by this study adds to our understanding of how species navigate their nutritional environment in the lean season and how vulnerable the species may be to large changes in their environments as they appear to be existing on the edge already.

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