Diet, activity patterns, foraging movement and responses to deforestation of the aquatic tenrec Limnogale mergulus (Lipotyphla: Tenrecidae) in eastern Madagascar

Authors


All correspondence to: J. P. Benstead. E-mail: benstead@sparc.ecology.uga.edu

Abstract

The aquatic or web-footed tenrec Limnogale mergulus is a semi-aquatic lipotyphlan insectivore 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 radio-tracking 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. Radio-tracking of two individuals indicated that Limnogale is strictly nocturnal and remains in streamside burrows during daylight. 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 used by the two aquatic tenrecs during each radio-tracking 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.

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