Body condition scoring of white (Ceratotherium simum) and black rhinoceros (Diceros bicornis) in European zoos

Abstract

White (Ceratotherium simum) and black (Diceros bicornis) rhinoceroses differ in ecology and sociality, which is reflected in their ease of care in zoos. Zoo-housed black rhinos are susceptible to unusual diseases that have hypothetically been linked to obesity. We applied published body condition scores (BCS; 1-5) to 84 adult white and 57 adult black rhinos living in 41 European zoos, established our own BCS protocol with overview scores and scores for individual body regions, based on our ability to distinguish scores on photographs, and related these to husbandry conditions. Exact body mass was available for 17 and 20 white and black rhinos, and was estimated for the rest. Scoring was conducted by one single observer, twice in a blinded manner. White rhinos were kept in larger enclosures and received a lower proportion of non-forage feeds than black rhinos. Contrary to previously published BCS protocols, the protocol presented here, achieved a distinctively higher number of identical scores at repeated scoring from photographs for all evaluated body regions. BCS were generally positively correlated to body mass, but were not related to the percentage of non-forage feed in the individual diets. White rhinos had higher scores than black rhinos (e.g., BCS overview side 3.83 ±0.76 vs. 3.39 ±0.85), suggesting that obesity, if at all, is more common in white rhinos. Additionally, BCS were relatively independent of age in white rhinos but declined in black rhinos with age, supporting concepts of chronic, accumulating health problems in black rhinos. In black rhinos, BCS were lower in animals with impaired dental status compared to animals without such alterations. In both species, males tended towards lower BCS compared to females. BCS had no effect on female black rhinos breeding status, but tentative evidence suggested that non-breeding white rhinos show higher BCS. Our findings do not support concepts that associate black rhino health problems with obesity, but emphasize the relevance of strategies for maintaining long-term health.