or woodland habitats. The number of active runways intersecting a line transect of fixed length
can be used as an index of abundance. Activity of runways can be determined by the presence of
fresh scats or fresh plant clippings.
Advantages and disadvantages
The advantage of track counts is that they are a cheap way of determining the relative abundance
of wide-ranging carnivores that live at low density. The disadvantage is that all these measures
confound activity with abundance; so, if the index increases, it could be because of higher activity,
higher abundance, or both. Territoriality in some carnivores may affect the use of trails, and the
spatial design of the sampling programme for tracks must take into account the size of the home
range of the species under study.Wilson and Delahay (2001) review these methods in more detail.
Biases
All indirect methods of census are best if they can be validated with a population of known
size. This has been impossible with most of the cases in which track counts have been used, and
consequently it is not possible to estimate bias. The best recommendation is to keep the design of
the surveys constant with respect to environmental and seasonal conditions, and to train observers
carefully in track identification.
Hair tubes and hair catchers
Method
Hair tubes are long tubes slightly larger in diameter than the species being studied, with sticky tape
on the inside so that hairs are left on the tape as the animal passes through the tube (Lindenmayer
366 Mammals
et al. 1999). For larger mammals barbed wire or other sticky devices can be used to sample hair
from individuals without needing to capture them (Mowat & Paetkau 2002).
Advantages and disadvantages
The critical assumption is that the hair can be identified as to species or species-groups (Harrison
2002). Keys to mammalian hair are available for many groups (Brunner & Coman 1974; Day
1966; Staines 1958; Wallis 1993), These keys are not necessarily complete, and we recommend
that a reference collection be prepared for the species being studied. Keys may represent only
hairs from the dorsal surface and colour patterns of species may vary geographically. In addition,
there is variation in hair samples from different parts of the body of mammals. Some species
cannot be distinguished from hair alone.