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lunes, 25 de julio de 2011

Plots, physiology, and pair bond doubts

Research conducted by Greg Goodfellow, our behavioural intern, is not only beginning to bare fruit but has also thrown up some surprising, yet intriguing, records. He is working his way through the required data collection from each of the 9 measured locations within each of his 4 study groups. At present, although not yet statistically tested, it appears Greg is correct on some of his hypotheses over white-rumped tanager duets, territorial, and mate defence behaviours.
As there has been little, if any, previous work conducted on these birds it was always likely Greg would observe and record surprising incidences we would class as ‘unusual’. Of course these events are almost certainly not unusual. Rather it is a testament to how poorly we understand these Cerrado dwelling animals. For example, recently Greg observed and recorded some ‘unusual’ social behaviour within one of his study groups. On one occasion he recorded the resident male dueting with two different females at two different times. Furthermore, within the same group, Greg later recoded the same male dueting with two females at the same time. These observations underline not only how little we know about this species but also how flexible animal social systems can often be. Currently white-rumped tanagers are classified as a monogamous pair-bonded species. Greg’s recent records place question marks over the current opinion and may suggest higher and more direct levels of same sex competition or multiple group members taking part in synchronised song. Genetic data will cast more light on this issue.

Our botany intern Georgina Snelling is now two weeks into her field investigation on the factors affecting fern abundance, diversity, and distribution within the Para la Tierra reserve. Over the last 14 days Georgina has successfully measured and GPS’ed three 100m x 100m survey plots in each of her study habitats – Monte seco (dry forest), Atlantic forest, Cerrado, and riparian. This gives her a total of 12 plots to collect data from. Additionally, in the last two weeks Georgina has found two new fern species that she was previously unaware of, thereby adding to the known diversity within the reserve.

Aimee Oxley continues to press ahead with her Masters research into the affect of habitat disturbance on small mammals. Recently she has been trapping a higher than normal rate of the rarer species of Atlantic forest small mammals, for example Oligorysomys nigripes and Oligorysomys fornesi. Her research is also showing that weather and climatic conditions do have a distinct affect on her capture rate. During our recent warm and dry spell the number of daily captures fell from an average of over 15 to under 5. However, when we recently experienced a couple of storms the capture rate rocketed again. Currently the opinion is that during wet and/or cold conditions small mammals will be more likely to seek out shelter, and traps are a good form of shelter.


Behaviour among Cyanocorax chrysops (plush-crested jays)
As traditional methods of bird catching, such as mist netting, have failed with the Plush-crested jays we are now going to begin building custom cage traps. These will include bait at one end with a trigger system to close the door either when the bird pecks at the bait or steps into a trip wire. Furthermore we are honing in on what foods will tempt the jays into the traps. Our local forest guards have suggested that these jays have a particular liking for eggs and peanuts. So I will combine these two foods with the cultivated maggots to try and produce an irresistible plata.
I am now into the last two weeks of data collection for this initial phase of the project. Once this has been completed the focus for this project will switch to producing the first behavioural publication of Plush-crested jays and also catching and fitting individual leg rings to all group members. Then this project can progress to more complex issues.


Social and ecological factors among Clyomys laticeps (broad-headed spiny rat).

As I write the final round of root sampling is drying in the oven. In 3 days from now we will be in a position to either confirm or reject our hypothesis on water content as a factor for the apparent relationship Clyomys holds with a particular Cerrado bush. The root systems for all three of the sample bush species are unusual. None of these species, and hence probably many more Cerrado species, exhibit a tap root. What they do show is an extensive and large network of lateral long roots that sometimes stretch up to 5 meters away from the above ground section. This is seen even for very small bushes that appear to be in the primary stages of growth. A possible explanation for these observations is that many, if not all, of the Cerrado flora species can preserve their root systems during the natural fires that occur in this habitat. By doing this the plant essentially stays alive and can re-sprout once the fires have succumbed. Over a number of years of doing this the plants can continue to grow their roots without loosing them.
As I said in my last blog we are preparing to look at nutrient and compound levels in these bushes as an alternative explanation for the perceived preference Clyomys has for a particular species. Along with this we plan to dissect a Clyomys specimen from our museum to see if this species has a derived adaptation in the kidneys for retaining water. Trapping the Clyomys will begin in early August.

Until next time ill say goodbye.

Best wishes,

Luke

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