Key words: activity patterns; diet; Limnogale mergulus; Madagascar; Tenrecidae.
ABSTRACT: The aquatic or web-footed tenrec Limnogale mergulus is a semi-aquatic
lipotyphlan known only from stream habitats of eastern Madagascar. Limnogale
is considered a high conservation priority because of its rarity, suspected
vulnerability to habitat degradation, and unique ecological niche on the
island. However, its ecology and behaviour remain poorly understood. Quantitative
faecal analysis and radiotracking were used to study the diet and foraging
activity of Limnogale in eastern Madagascar. Faecal pellet counts along
forest and zero-canopy streams were also conducted to examine the response
of aquatic tenrec populations to catchment deforestation. Faecal analysis
indicated that the diet of Limnogale consists mainly of larval and adult
aquatic insects, larval anurans and crayfishes. The most important prey
were Ephemeroptera, Odonata and Trichoptera larvae. Diets did not differ
substantially between forest and zero-canopy streams. Radiotracking of
two individuals indicated that Limnogale is strictly nocturnal and remains
in streamside burrows during daylight hours. Nocturnal movement was restricted
solely to stream channels and consisted of active foraging by swimming
and diving. Distance travelled per night ranged from 200 to 1550 m along
the stream channel (means 1067 and 860 m, respectively). The total lengths
of stream channel utilised by the two aquatic tenrecs during each radiotracking
study were 1160 and 505 m, respectively. Faecal pellet counts along forest
and zero-canopy streams suggested that Limnogale was at least as abundant
in zero-canopy streams. This finding suggests that Limnogale is not an
obligate forest species; however, it preys on benthic communities that
are extremely vulnerable to sedimentation. Control of excessive sedimentation
and maintenance of healthy benthic communities are essential to Limnogale
conservation. We include an updated list of known sites for Limnogale and
recommend the use of faecal pellet surveys to assess the current distribution
of the species.