Gliding performance of the red giant gliding squirrel Petaurista petaurista in the tropical rainforest of Indian eastern Himalaya

Gliding squirrels occur globally and many are of conservation concern due to habitat fragmentation and degradation. Information on their ability to cover the distance between two trees by gliding is lacking in many species which might be vital for habitat management and conservation. The aim of the study was to present the field observations on gliding behaviour of the red giant gliding squirrel Petaurista petaurista observed within tropical rain-forest of Namdapha National Park, Arunachal Pradesh, Indian eastern Himalaya. The data were collected on 71 glides observed at nights. The mean height of launching and landing trees were 28.5 +/- 1.0 m and 16.4 +/- 0.9 m, respectively. Gliding variables calculated were vertical drop (mean = 13.4 +/- 1.0 m), horizontal distance (mean = 36.3 +/- 2.7 m), air speed (mean = 8.9 +/- 0.2 m s(-1)), ground speed (mean = 7.9 +/- 0.2 m s(-1)), glide ratio (mean = 3.1 +/- 0.2), glide angle (mean = 19.0 +/- 0.9 degrees), GBH of launching tree (mean = 156.8 +/- 8.5 cm) and GBH of landing tree (mean = 195.2 +/- 9.5 cm). Gliding distance was categorized in four types. The highest glides in a 26-50 m glide-class (44% (n = 31)) were the most frequently observed. Gliding squirrels preferred top canopy (56%, n = 40) for distant glides. Forest structure has an influence on the gliding habits of gliding squirrels and thus our data on gliding parameters should be used when planning forest management actions.