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The 70 south and southeast Asian snake species in the genus Oligodon are known as "kukri snakes", the name being derived from a distinctively shaped Nepalese knife, the kukri. The hind teeth of these snakes are broad and strongly recurved, much like the shape of the kukri. These non-venomous snakes are usually nocturnal and often brightly colored. They feed primarily on the eggs of birds and reptiles. The morphology of their teeth is well suited for opening eggs. These snakes enthusiastically ingest the contents of opened eggs presented to them, as well as ingesting small reptile and bird eggs whole. To take eggs that are apparently too large to swallow, a kukri snake uses its uniquely shaped teeth and jaw articulation to saw a hole in an egg shell that is large enough for it to insert its head and feed on the contents of the egg. Stomach content studies have revealed that kukri snakes also eat small rodents, tadpoles, frogs, and insects. Juveniles appear to be primarily insectivorous. It is not known whether they hunt or scavenge for food. (Green et al. 2010 and references therein)
Oligodon has been a taxonomically challenging group. Green et al. (2010) undertook a mtDNA-based molecular phylogenetic analysis of Oligodon snakes and examined congruence between the resulting phylogeny and hemipenial characters. Green et al. found that the hemipenial morphology of Oligodon appears to be phylogenetically constrained and, therefore, informative. The hemipenes are useful in species identification, and Green et al. speculate that the ornamented organ may even play a role in speciation or maintenance of species. Phylogenetic relationships suggested by Smith based on hemipenial morphology (1943, cited in Green et al. 2010), were supported by the analyses of Green et al. (2010). Green et al. emphasize that descriptions of new Oligodon species should be based on a type series that includes males with described hemipenes.
Much confusion in Oligodon occurs because of extensive intraspecific variation in color and patterning. Although most species of Oligodon have a fairly invariant color pattern, a few species (notably O. cyclurus, O. fasciolatus, O. cinereus, and O. taeniolatus) are highly variable. The highly variable species are also widespread. Oligodon cyclurus and O. fasciolatus range from India eastward through Thailand (at approximately 11°15′N), to Vietnam and southwestern China (Yunnan). A separation of about 500 km on the Thai peninsula separates O. fasciolatus from O. purpurascens, which continues throughout Indonesia. The distribution of O. cinereus closely matches cyclurus+fasciolatus. Ologodon taeniolatus ranges throughout India to eastern Iran and northward to southern Turkmenistan.
According to the molecular phylogenetic and morphological investigation by Lei et al. (2014), Oligodon multizonatum, a Chinese endemic species known only from Sichuan and Gansu Provinces, may not belong in Oligodon at all, but rather in the still somewhat poorly defined genus Lycodon
Green et al. (2010) provide an excellent entry into the literature on Oligodon.
(Green et al. 2010 and references therein)
