How can climate change affect lemurs and cetaceans?
Climate change and lemurs
Dr Pat Wright and Summer Arrigo-Nelson (Madagascar's Lemurs) along with a number of researchers working in Ranomafana National Park, Madagascar have discovered a plausible link between rapid climate change and reproductive success in the Milne-Edwards' sifaka (Propithecus edwarsi). The research, related to dental senescence - the process of dental ageing, uses advanced GIS (Geographical Information Systems) technology and tooth imprints from sedated lemurs to build up a picture of the wear and tear on a female sifaka's teeth over the course of its life.
They found that these lemurs, with a maximum lifespan of more than 27 years, maintain healthy dental function until around 18 years of age. Beyond this, dental function worsens as teeth are eroded.
While fertility remains high in older lemurs the research has found a link between dental senescence and reproductive success. Beyond the age of 18 yrs, it was found that mothers' infants only survive if lactation seasons have elevated rainfall. The reasons for this are intuitive. The milk of many lemurs - including this sifaka - is very dilute. Further, the sifaka appears to obtain all its water through its diet. If dental function is inhibited, additional effort is required to process the same amount of food. Combine this with unfavourable rainfall and the inference is that milk lactation and infant survival will be affected.
While further work is needed to elucidate exactly how dental senescence may affect infant survival, field observations have shown that apart from infanticide, infants tend to die after exhibiting general weakening. This conforms to the above hypothesis. In addition the work showed that although infants of young females survive even during years of little rain during lactation, infants of old females appear to require 5mm of rain per day to survive past one year of age. Significant correlation between rainfall and infant survival of dentally senescent mothers suggests senescence is key factor in linking infant survival to rainfall.
The field data used to support this work has been gathered over 20 years using rainfall as an indicator of environmental quality in addition to a suite of behavioural and physiological measurements. Perhaps surprisingly, during the 20 year study an average of 14% of adult sifakas were passed their dental prime indicating that long-lived individuals may play an important role in population growth. Findings like this are only possible with a long-term funding commitment, something that Earthwatch is known for and will continue to strive to achieve.
The implications of this research are perhaps more profound. The team predicts that the effects of dental senescence on reproductive success may be more pronounced in mammals living in seasonal habitats. While other evidence suggests that the onset of dental senescence in baboons and koalas affects reproductive success in these species, in time we may be looking at a more general trend whereby over ecological timescales, the tendency for mammalian females to live beyond their reproductive senescence may indicate and render endangered rainforest species vulnerable to rapid climate change.
Climate change and cetaceans
Climate change is affecting the marine environment of the North-East Atlantic. But how and why? These are questions that Earthwatch scientists are trying to answer as they study the effects of climate change on large mammal and fish populations around the UK coast.
Four projects looking at the ecology of seals, dolphins, whales, porpoises and basking sharks are adding new insights into distribution, abundance, phenology and behaviour of these species which may be related to climate change.
For example; a shift in plankton density and composition in the North-East Atlantic may have repercussions for basking shark and seabird populations in Western Scotland. Changes in the ecology of these higher trophic species are already being seen. Though direct cause-effect is difficult to prove, continued monitoring as well as focussed research is essential to understand the complex changes that are taking place. Earthwatch has an important role to play in this providing the volunteer and financial resources to make this research possible. With two projects in Scotland looking at cetacean ecology, a project in Cornwall and Scotland looking at the distribution and abundance of basking sharks (Cetorhinus maximus) and a project in Cornwall assessing the status of the Grey seal (Halichoerus grypus), Earthwatch will continue to make a valuable contribution to understanding the changes that are taking place.
Climate change is a priority area for Earthwatch as we strengthen our research portfolio to provide the objective research vital for decision makers to address the complex and potentially emotive issues associated with this phenomena. Climate change is currently on agendas across the board and Earthwatch will continue to engage audiences, provide resources and promote the understanding and action necessary to address the challenges ahead.