The proposed Parc Regional de Belomotse - Frontier-publications ...

Rattus rattus has been shown to be a harmful pest, bringing several diseases to
Madagascar. One of these diseases, plague, which is carried by the fleas of R. rattus,
only occurred on the island after the introduction of rats. Today, the disease is still a
problem, affecting approximately 800 humans every year (S. Goodman, pers. comm.,
2002). Furthermore, other parasites and viruses carried by this animal have caused
severe problems for native rodent species. With little immunity to these exotic
diseases, populations have decreased and several species may have been driven close
to extinction as a result. The endemic rodent Eliurus myoxinus was found in low
numbers in the surveyed sites compared to the introduced rodents R. rattus and Mus
musculus. Comparatively little is known about the populations of E. myoxinus in the
region, and further surveys need to clarify whether the low density observed is normal
for the species, or whether it is suffering from competition with the introduced
species.
The pygmy musk shrew, Suncus madagascariensis, from the family Soricidae, has
been found during the survey. This species is the world’s smallest terrestrial mammal,
with a head-body length of 50- 55 mm and a weight of 3-4 g (Garbutt, 1999).
However, the individuals that were captured during this survey were all considerably
smaller, with a head-body length of 35-40 mm and a weight of approximately 2 g.
The endemic status of this species is uncertain, but it is currently assumed that the
populations on Madagascar are introduced (S. Goodman, pers comm). This species
was commonly found both in gallery and spiny forest habitats, but the impact of the
species on native species of rodents and tenrecs is not known. Being insectivorous, it
may compete with other small insectivores for food.
The introduced ungulate Potamochoerus larvatus larvatus occurs along the west coast
of Madagascar. Spoors were found both in marshy and in forested areas within the
surveyed areas. This species poses a threat to some native species in these habitats. It
forages vigorously in the undergrowth, digging up the soil as it feeds on roots, fruits,
invertebrates, vertebrates and bird eggs. It is also known to feed on tortoise eggs.
The introduced civet, Viverricula indica, is potentially harmful as it preys upon a wide
variety of native animal species, particularly small vertebrates. V. indica was observed
in several locations throughout the surveyed areas, often near to villages.
5.4.3 Seasonal variation
Due to the arid climate in the region, some animal groups tended to lower their
activity during the dry season, when much of the vegetation dried out and food
sources became scarce. However, rodents appeared to stay active all year round and
were observed regularly throughout the year in all surveyed areas. They were trapped
in higher numbers during the dry season than during the wet season, see figure 4.
Being omnivorous and opportunistic in their feeding behaviour, rodents can survive
on a wide variety of food items, e.g. fruits, seeds and invertebrates, which will allow
them to be active at times where other groups are inactive. Stephenson (1994) found
the same levels of activity in a year-round trapping survey in central Madagascar. He
suggested that due to the abundance of ‘natural’ food sources in the wet season, the
trap bait seem less attractive to the animals, so trapping success for rodents is reduced
at this time. This hypothesis explains the high trap success during the dry season in
the present survey, with the accompanying dip in trapping during the wet season.
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