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Comparative Endocrinology

The comparative approach represents an important tool for studies in evolutionary biology. By helping to understand species differences in reproductive patterns, it provides us with useful insights into the adaptive significance of reproductive processes as well as their underlying control mechanisms. The availability of non-invasive methodologies suitable for multi-species application and our work promoting field endocrinology as an important new discipline in primatology, has opened up exciting new possibilities for comparative investigations.

There are 3 main aspects to our work in this area:

 

(c) DPZ, 2008 (Laboratory Work)
Susilo Hadi from Gadjah Mada University (Yogyakarta) receiving training in methods of faecal hormone analysis. As part of a joint venture with the AIM Zürich we are also engaged in establishing a non-invasive endocrine laboratory at the Agricultural University Bogor to support studies in wildlife biology in Indonesia.

Reproductive diagnostics
    
Our hormone assay facilities support a wide range of methodologies for the measurement of steroid hormones, primarily in urine and faeces. These facilities, together with our pioneering work in the development of methods of non-invasive assessment of physiological status provide the basis for an extensive endocrine diagnostic service for zoos and the international scientific community at large as well as serving an important function in training and technology transfer among our collaboration partners. Of course, our hormone laboratory also assists the work of other research units within the German Primate Centre and provides essential support for our own comparative and field based research programme.

Reproductive variation
    
Primates exhibit an unusual degree of variation in reproductive characteristics, much of which remains overlooked and unexplained. Non-invasive methodologies are helping us to explore the physiology underlying species differences in ovarian cycle characteristics and gestation length and to better understand the adaptive significance of the extensive variation that we see.   

(c) Daffner (Mouse Lemur Sonograph)
Ultrasonographic picture of a mouse lemur foetus on day 29 of the 64 day gestation period. At this stage, the foetus has a crown-rump length of ca. 9 mm (indicated by yellow dots, head on the left) and heartbeat is detectable.

One group of particular interest in this respect are the strepsirhine primates (lemurs, lorises) which not only show extreme variation amongst each other, but also differ substantially from their anthropoid counterparts.

In one ongoing project with Roehampton University, UK, we are investigating patterns of embryonic and foetal development in relation to endocrine profiles during gestation in various species of lemur in order to characterise reproductive life history variables in these primates.

Endocrine measures of environmental stress
    
Since increased stress impacts on both health and reproduction, the assessment of stress physiology in free-ranging primate populations has important implications for conservation and animal welfare. In this respect, faecal glucocorticoid measurements may serve as a useful bioindicator for health and survival probability of potentially threatened populations. Our ultimate aim is to investigate the link between environmental stress and reproductive parameters in wild primate populations.

(c) Tuanan Orangutan Research Project AIM-UZH, 2003 (Orangutan with child)
Orang utans, like many other primate species, are threatened by anthropogenic disturbance and large-scale habitat loss. To what extent these environmental factors are associated with chronic stress and how this might affect reproductive health of populations is one focus of our studies.

Ongoing collaborations include a project with the Anthropological Institute of Zurich University to investigate the effect of environmental variables (rainfall, food availability, forest type, degree of human disturbance) on stress hormone output in wild Sumatran and Bornean orang-utans.
    
Along similar lines, we are collaborating with Durham University, UK, to examine the impact of human disturbance and wildlife ecotourism on the stress physiology and health status of the critically endangered western-lowland gorilla (Gorilla gorilla gorilla). We are also involved in a project with the Vetsuisse Faculty University of Zurich to clarify the potential role of stress in the poor captive breeding success of the pileated gibbon.