Cryptic Creatures: Assessing the Habitat Requirements of Difficult to Find Animals

            When attempting to determine suitable conservation practices for any species, a solid knowledge of their habitat requirements is an absolute necessity. Habitat suitability models then use factors such as land use, topography, and elevation, generally analyzed through computer programs such as GIS, to assess how well a species may do in a particular area. Similar analyses can be done by using presence-absence data.

Figure 1. Sighting records of Dendrolagus lumholtzi around Yungaburra, QLD, Australia.

These records can then be correlated with habitat data to assess the probability of a species’ occurrence at other points in the landscape. However, for cryptic or rare species, such information may not be readily available, or only partially complete.   

One study on the habitat use of a cryptic species focuses on the Lumholtz’s Tree Kangaroo (Dendrolagus lumholtzi). The Tree Kangaroo is an arboreal folivore endemic to the rainforests of the Atherton Tablelands of Queensland, Australia. In 2011, Heise-Pavlov et al. assessed Tree Kangaroo habitat use through a grid-based analysis of a segment of Complex Notophyll Vine Rainforest. At each grid section, they measured tree diameter as well as Tree Kangaroo activity, as determined by their distinctive fecal pellets and tree scratch marks.

Figure 2. Identifiers of Lumholtz’s Tree Kangaroo activity. (a.) Scratch marks left by Tree Kangaroo on tree bark. (b.) Tree Kangaroo fecal pellet.

They found that signs of Tree Kangaroo activity are more heavily concentrated on trees with a smaller diameter, as well as ones with fewer obstructions along the trunk, such as epiphytes and lianas. Trees fitting this description would likely allow for quicker or easier movement along the tree trunks, potentially enabling a more successful retreat from predators. Heise-Pavlov et al. concluded by recommending a focus on enlarging and connecting existing rainforest fragments as a means of providing less complex, and therefore more suitable, habitat for this elusive species.

            While this certainly illustrates the importance of appropriate climbing trees to the habitat requirements of the Lumholtz’s Tree Kangaroo, there are still many other factors that should also be considered. While Tree Kangaroos may prefer smaller, less cluttered trees for traveling to and from the canopy, it does not take into account their preferences once they are already up there. Tree Kangaroos have often been observed both resting and feeding in larger, older trees, indicating that these “feed trees” may also play a substantial role in Tree Kangaroo habitat selection. In addition, indirect presence indicators such as scratch marks and scat form only an incomplete picture of the area utilized by the Tree Kangaroos. Therefore, any future studies on the habitat requirements of the Lumholtz’s Tree Kangaroo would do well to look further into not only what constitutes Tree Kangaroo habitat, but also into more effective detection methods, as a more solid knowledge base on both where they currently are and where they are capable of living would be beneficial in implementing better conservation strategies for this cryptic and charismatic species.

References:

Heise-Pavlov, S.R., Jackrel, S.L., & Meeks, S. (2011). Conservation of a Rare Arboreal Mammal: Habitat Preferences of the Lumholtz’s Tree-kangaroo, Dendrolagus lumholtzi. Australian Mammalogy, 33, 5-12.