A Case Study of the Molecular Genetical Diagnosis of a Small African Elephant (Loxodontasp.) “Nana” Kept at Asahiyama Zoo

Abstract

The African elephant genus Loxodonta consists of two distinct species, savanna elephants (Loxodonta africana, Blumenbach 1797) (Fig. 1A) and forest elephants (Loxodonta cyclotis, Matschie 1900) (Fig. 1B) (Grubb et al. 2000; Roca et al. 2001, 2005). The savanna elephants are widely distributed in bush areas of the sub-Sahara and their body sizes are larger than those of the forest elephants. On the other hand, the forest elephants inhabit tropical rain forest areas of Central Africa and the coastline of the Gulf of Guinea in West Africa (Nowak 1999; Grubb et al. 2000). There are several morphological differences between them (e.g., the shape of the cranium, ears, tusks, body build and so on; Grubb et al. 2000). However, occasionally there are individuals for which it is difficult to identify the species (Groves and Grubb 2000; Debruyne 2005). The forest elephants are endangered and adequate breeding plans in zoological gardens are urgently needed. Therefore, accurate identifications of the species are important. The conventional method of species identification used in Japanese zoological gardens, however, has some problems. A small female Loxodonta named “Nana” (died on April 21st, 2006) was being kept as a forest elephant at Asahiyama Zoo (Asahikawa City, Hokkaido, Japan) (Fig. 1C). She was a wild-born individual (geographical origin unknown), and was purchased in 1980 at the approximated age of 2–3 years old. At first, she was considered to be a savanna elephant, but later features attributed to a forest elephant were identified in her morphological characters. Firstly, her body size was small. Secondly, she had the same hoof structure as forest elephants (5 hooves on the forelimb and 4 on the hindlimb). Thirdly, her ears overlap across the top of the neck. From these reasons, she was identified as a forest elephant. But uncertainties to this identification remained. For instance, it is generally said that savanna elephants have 4 hooves on the forelimb and 3 on the hindlimb (Nowak 1999), and forest elephants have more hooves on both the forelimb and hindlimb (Debruyne 2005). However, it is known that there are variations among the African elephants (Sikes 1971; Grubb et al. 2000). The savanna elephants have 4 or 5 hooves on the forelimb, and 3 to 5 on the hindlimb. Corresponding numbers for the forest elephants are 5 hooves on the forelimb, and 4 to 5 on the hindlimb (Sikes 1971). Therefore, the number of hooves cannot be a diagnostic character of the species in this case. Concerning the ear shape, the character described above is rather that of the savanna elephants than that of the forest elephants (Grubb et al. 2000). In addition, concerning the body build of the African elephants, the back of the savanna elephants tend to be markedly concave, and that of the forest elephants tend to be nearly straight (Grubb et al. 2000; see also Fig. 1A and B). The back of Nana was relatively concave (Fig. 1C). In Japan, there were three forest elephants (e.g., JAZA 1991; Nana of the Asahiyama Zoo, Mari of the Tokuyama Zoo, and Bebe of the Okinawa Kids Discovery Kingdom), and all of them were identified as forest elephants mainly based on the body size and hoof structure (in the case of Bebe, the nearly linear back and rounded ears were also used). As we mentioned above, it