The butterflies of IITA

Robert Warren,

Charaxes imperialis. Photo by IITA.
Charaxes imperialis. Photo by IITA.

IITA boasts a wide range of butterflies. Knowledge about the diversity of these species, however, is incomplete. For instance, a preliminary survey conducted from 2002 to 2009 has confirmed the presence of 149 butterfly species. The actual number could fall somewhere in the range of 250 to 400.

A survey carried out in a directly equivalent location (Olokomeji Forest Reserve) in the late 1960s found 267 species, with quite limited collecting inputs (estimated total >450). A more complete survey at Agege, near Lagos in southwestern Nigeria, found more than 380 species. This location is in the moist evergreen forest zone, and is fairly comparable to the secondary nature of the IITA forest.

Completing a survey at IITA would yield information useful for conservation. The fact that the IITA forest is small and now isolated would allow the assessment of pressures on extinction. Despite the enormous destruction of West African forests to date, records show that butterfly extinction has yet to occur when viewed on a regional scale.

While the primary consideration for survival will be the presence of the host plants, there is also a consideration of the range required for survival. Knowledge of the total species population within IITA and specific species present could be likely to provide answers on the cut-off point where the range is too small for survival of certain species groups.

The IITA forest is also an important conservation target itself because of its location. It is quite possibly the westernmost representative of semi-deciduous forest on this scale before the Dahomey gap. Attempts to locate equivalent forests within Nigeria to the west of IITA, guided by satellite imagery, yielded only one small, unprotected patch (5 km west of Tapa). Forest reserves have all but disappeared. Several butterfly species (e.g., Liptena ilaro, Euriphene kiki, Axiocerses callaghani) found near IITA have not been seen elsewhere, pointing to the biogeographical importance of such habitats. If results eventually show that the IITA forest is indeed too small to allow the survival of all the species that should be present in an equivalent forest type, it will nonetheless remain an important refuge.

Display cases of all but a handful of the 149 species observed to date have been donated to IITA to promote further interest.* A specimen of the very rare species Melphina noctula was found at IITA (there are only three in the Natural History Museum), and has been donated to the African Butterfly Research Institute in Nairobi, Kenya.

An in-depth study of the IITA butterflies would be of international interest and importance because very few such surveys have been completed in Africa. Comparison with our knowledge of the fauna of western Nigeria could shed light on the importance of a forest such as IITA’s for the long-term survival of species. It could be one of the localities proposed for studying the survival of the butterflies between now and 2100. Finally, it could show if new species are added as the forest matures from its secondary status over time.

*Specimens were collected, identified, mounted, and donated recently by the author to IITA. These are currently on show at the IITA International School in Ibadan, Nigeria. The author is a buttefly expert who came to Nigeria at the age of 4 months. He has been surveying butterflies all over Nigeria and also at IITA since 2002.