Fecal Pellet Measurements of Manipur Brow-Antlered Deer With Respect to Sex and Age Classes

1. What they did

The Manipur brow-antlered deer is the most endangered subspecies of its species. The only wild population, about 50 animals, lives in a small area beside Loktak Lake in Manipur, India, and they are hard to see because they are secretive, evasive and live in habitat that is hard to get into. The authors wanted an indirect way to learn about the population, so they asked whether the size and weight of droppings could tell males from females, and young animals from old.

• The animals. 12 captive deer at the National Zoological Park in New Delhi: 7 males and 5 females, in different age classes. Males were placed in classes 0, 2, 3 and 4 by antler growth (for example, class 4 stags have a main beam of about 8 to 10 cm with finger-like projections). Females were placed in classes 2, 3 and 4 by body size (class 2 is 1 to 2 years old, class 3 subadult, class 4 adult-sized).
• Collecting droppings. Fresh pellets were collected from each animal early every morning for 7 days in December 1989. The deer were fed green fodder and a ration mixture.
• Measuring. Pellets were oven-dried at 70°C for 3 days. Ten randomly chosen pellets per animal were measured for length and maximum width (to the nearest millimetre, with a Vernier caliper) and weighed (to the nearest 10 mg).
• Analysis. Analysis of variance (ANOVA) compared age classes, and t tests compared pairs of sex and age classes.

2. What they found

Males

• Pellet length did not change from age class 2 onward.
• Pellet weight rose up to class 3, then stayed about the same.
• Differences between age classes were significant for width and weight, but not for length.
• Length and weight varied more between pellets than width did.

Females

• Pellet length rose from an average of 12.2 to 14.2 mm, and weight from 0.22 to 0.46 g, as females got older.
• Differences between age classes were significant for all three measures.
• Weight varied more between pellets than length or width did.

Both sexes

• Pellet width increased gradually from class 2 onward.
• Comparing males and females of different age classes, at least one measure differed significantly in every pair tested. For example, young males (class 2) differed from young females (class 2) in length, width and weight, while adult males (class 4) differed from adult females (class 4) only in length.

3. What they concluded

• Pellet measurements may help tell the sexes apart in wild deer, and to some extent their ages, by using a combination of length, width and weight.
• The method could be useful for monitoring both the existing wild population and a proposed second population, of captive-bred deer, in Pabitara Wildlife Sanctuary in Assam.
• It is not yet known whether seasonal changes in the diet of wild deer would change the size or weight of their pellets. Studies varying the diet of captive deer could answer this.

4. How tracking was or was not used

There was no tracking in the field. The study tested scat measurement as a way of reading tracks and signs: droppings from known captive animals were measured to see whether pellet size and weight reveal the sex and age of the deer that left them.

6. Other technologies, skills or innovations

• Vernier caliper for pellet length and width, and an analytical balance (Mettler) for dry weight.
• Age classes of stags judged from antler growth, following Schaller (1967) and Barrette (1991).

7. Implications for conservation (from the paper)

• The deer are hard to locate in the wild, so indirect methods such as droppings are urgently needed to learn about their distribution and numbers.
• Pellet measurements could help monitor both the existing wild population and reintroduced, captive-bred deer.