Prey and Nutritional Analysis of Megaderma lyra Guano from The West Coast of Karnataka, India

Microchiropteran bats play a vital role in the ecosystem. They consume large volumes of insects many of which are agricultural pests and their droppings (guano) contain large amount of partly digested insect parts that form the resource base for other diverse form of consumers in the food chain including diverse microbes. These together make guano the best organic fertilizers. However, food habits of different species of bats vary depending on the species, locality, season and the ability of the bat to detect certain types of insects using morphological characteristics. Hence, an attempt is made in the present study to analyze the seasonal variations in the food habit of a microchiropteran bat, Megaderma lyra, so as to determine the insects on which they feed and also to do a nutritional analysis that include the moisture , carbohydrate, protein, lipid, ash, nitrogen, phosphorus and potassium content of their guano. The study was carried out during November 2009 to October 2010 in a maternity colony in an abandoned house which is mainly surrounded by coconut plantations and paddy fields. It is located at Karkala in D.K. district of Karnataka. To determine their insect prey, insect parts present in the bat guano were identified to ordinal level. The percent volume and percent frequency of food items present were also determined and were classified as basic food (>20%), constant food (5-20%), supplementary food (1-5%) and chance food (<1%). During the sampling period insects belonging to 15 orders were identified. The scales of fishes, legs of frogs and hair, tooth and legs of rats recorded during pre monsoon, monsoon and post monsoon were all included under Vertebrates. Of the total insect orders identified, Coleopterans formed the major food items in all the three seasons (Premonsoon, monsoon and postmonsoon) and Vertebrates alongwith Coleopterans formed major food items during monsoon and postmonsoon. Whereas Hemipterans formed the constant food in all the three seasons and Lepidopterans formed the constant food along with Hemipterans during monsoon and postmonsoon. Other insect orders quantified included Dictyoptera, Trichoptera, Orthoptera, Diptera, Hymenoptera, Odonata, Ephemeroptera, Isoptera, Neuroptera, Dermaptera, Thysanoptera and spiders. The insect orders represented in the faecal pellets though not all indirectly reflect the occurrence of agricultural pests since their presence coincides with the type of vegetation surrounding the roosting site. Nutritional analysis of the guano revealed that the guano contained maximum carbohydrate (2.8%) during pre monsoon, lipid content (9.3%) during post monsoon and protein during pre monsoon and post monsoon (8.9%) period. N-P-K analysis revealed that guano is rich in phosphorus. Also phosphorus content was recorded highest in all the seasons (6-11%) and potassium during monsoon (1.3%) and post monsoon (1.2%). However, no significant variation in the nitrogen content was recorded. Therefore, the present study indicates that the Indian false vampire bat preys substantially on several insects injurious to crops, gardens and lawns and also on rodents. Further study is needed on the potential impacts of this and other insectivorous bats on these economic pests and also on organic enrichment of bat guano in the study area.