1 Tahrcountry Musings: The importance of tree hollows

Thursday, December 15, 2011

The importance of tree hollows

Tree hollows are of conservation importance for a Near-Threatened python species
G. L. Bryant, S. J. Dundas, and P. A. Fleming

Journal of Zoology

Volume 286, Issue 1, pages 81–92, January 2012

This is a very interesting paper that zeroes in on the great importance of the tree hollows with accent on ectotherms . These hollows provide micro habitats for many species. Understanding microhabitat requirements of species vulnerable to anthropogenic threats are very germane for conservation managers. There is definite decline in availability of this important microhabitat throughout the world.

In ectotherms, behaviour and physiology are strongly influenced by thermal conditions of microhabitat retreat sites.  Here the researchers identified retreat sites selected by south-west carpet pythons (Morelia spilota imbricata) through radiotracking 46 pythons over 3 years.  61% (22 of 36 individuals tracked over winter) used tree hollows as retreat sites (56% of all observations in winter), and remained in hollows for an average of 124 ± 49 (range 34 to 210) days. If pythons did not use tree hollows over winter, they found refuge in one of four alternative microhabitats: low vegetation cover (26% of winter observations), ground cover (10%), on tree branches (6%) or in hollow logs on the ground (2%). 

The researchers tested whether tree hollows provide a thermally distinct environment compared with alternative microhabitats. They found no difference in minimum, average, maximum or range of temperatures recorded between microhabitats. When they are inside the  tree hollows over winter, pythons had colder daily average and maximum body temperatures (cf. pythons that used other microhabitats), but this did not give them an energy saving . 

Pythons ate very little over winter and the researchers predict that animals sequestered within tree hollows do not access prey at this time. Tree hollows provide a critical refuge over winter when python body temperature is low, and their responsiveness is limited. At this time individuals are vulnerable to predation by terrestrial predators. Destruction of hollows through fire, land clearing, competition with other fauna species and the significant age required for hollows to form in trees all contribute to the decline in availability of this important microhabitat.


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