Osborn’s dwarf crocodile

Osborn’s dwarf crocodile, (Osteolaemus osborni), small crocodile species that inhabits the tropical forests and wetlands of Africa’s Congo River basin. The geographic range of Osborn’s dwarf crocodile extends from southeastern Cameroon and southwestern Central African Republic southward to the Republic of the Congo, the Democratic Republic of the Congo, western Uganda, and northwestern Angola. It is one of two formally recognized species of the genus Osteolaemus.

Osborn’s dwarf crocodile was first described, in 1919, as the species Osteoblepharon osborni, but, by the early 1950s, authorities had placed it in the species Osteolaemus tetraspis with dwarf crocodiles (also called African dwarf crocodiles; then classified as O. tetraspis tetraspis), where it remained as the subspecies O. tetraspis osborni for the duration of the 20th century. It was not until the results of an anatomical study were published in 2007 and the results of a genetic study were published in 2009 that Osborn’s dwarf crocodile was once again considered to be a separate species. This recognition is not universal: several sources continue to list the crocodile as a subspecies of O. tetraspis. Osborn’s dwarf crocodile is named for American paleontologist Henry Fairfield Osborn.

Natural history

Osborn’s dwarf crocodile is similar to the African dwarf crocodile in nearly all respects. Anatomically, between the two species there are only small differences in the skull. Males are generally larger than females (see also sexual dimorphism). The largest individuals have grown to 1.8 meters (about 6 feet) long with a maximum weight of 45.4 kg (100 pounds). However, most Osborn’s dwarf crocodiles are smaller; indeed, the smallest adult females have measured barely 1 meter (about 3.3 feet) long and have weighed as little as 13.6 kg (30 pounds). The top and sides of the bodies of both adults and juveniles have a prominent charcoal color, and the crocodile’s underside is lighter-colored, with yellowish cream bands on the lower jaw.

Like the African dwarf crocodile, Osborn’s dwarf crocodile is active mainly at night, and its diet is made up of small prey, including insects, insect larvae, and millipedes as well as small fish, amphibians, and mammals. It is vulnerable to larger predatory vertebrates at all life stages, but its primary source of mortality appears to be human beings, who hunt it for its meat and hide. The details involving the crocodile’s reproduction and development (that is, its courtship behavior, egg laying, parental care, and lifespan) are also thought to be very similar to those of the African dwarf crocodile.

Conservation status

The International Union for Conservation of Nature and Natural Resources (IUCN) makes no distinction between Osborn’s dwarf crocodile and the African dwarf crocodile, and thus it has yet to perform a population survey on the former. The organization classifies the African dwarf crocodile as a vulnerable species, on the basis of the most recent assessment, performed in 1996. The San Diego Zoo Wildlife Alliance notes that the African dwarf crocodiles of Gabon, the Republic of the Congo, and the Democratic Republic of the Congo (a region occupied largely by Osborn’s dwarf crocodiles) are common and widespread, with an estimated population density of more than 45.3 individuals per square km (72.5 individuals per square mile) in protected swamp habitats. Despite such anecdotal estimates, ecologists remain concerned that demand for the dwarf crocodiles’ meat as well as habitat loss from logging and land-use conversion to agriculture and other human purposes are causing populations to decline.