Here’s another ‘pod blog’, providing supplemental material for Episode 124: Herp Science Sunday with Justin Lee. In this episode of HSS, Dr. Alex Krohn and I had a conversation with Justin Lee, currently working on his PhD at the University of Michigan. The bulk of our conversation centered around the genus Oligodon, of which Justin is a subject matter expert. Justin has authored and co-authored a number of papers on Kukri snakes, describing new species, and producing an updated phylogeny of Oligodon in 2024. The material I am presenting here, including some of my Oligodon photos, supports the podcast episode; if you haven’t listened yet, I think it’s an entertaining segment featuring a very cool snake genus, and an up-and-coming young herpetologist. To begin with, let’s take a look at those specialized maxillary teeth that give kukri snakes their name.
The enlarged teeth in the back of the jaw are broad, and flattened, much like a knife blade. These bladed teeth allow kukri snakes to punch through and slice open the eggs of reptiles, and for some kukri snake species, the skin of toads and frogs as well. And let’s also have a look at the edged weapon that Oligodon teeth resemble, and are named after:
One of the publications we discussed during the episode was the 2024 phylogeny of Oligodon, which placed the possible origin of the genus to somewhere in Indochina around 25 million years ago. Over time, Oligodon has radiated across the bulk of southeast Asia, into the Indian subcontinent, and as far west as Iran.
The expansion of kukri snakes coincides with other events, including the spread of warm, wet forest habitats. A radiation of lizard species within the same time frame likely aided the Oligodon radiation, given their specialized diet of reptile eggs.
Our discussion touched on some of the interesting natural traits of kukri snakes, including their diet of reptilian eggs. Oligodon can swallow whole eggs of a certain size proportional to their head and body size, but their specialized dentition allows them to take advantage of too-large-to-swallow eggs as well – the snakes slash open the eggs, push their heads inside, and then drink (slurp?) the contents.
Another aspect of Oligodon that Justin, Alex, and I discussed was the evisceration of frogs and toads, and the consumption of their inner organs. While this has been documented in some species (a web search reveals a handful of gruesome images), it is not known how widespread the behavior is among the rest of Oligodon. It should be no surprise to listeners of the podcast that snake behaviors and other aspects of serpent natural history are in short supply. It seems to me that for kukri snakes, it is no great shift from opening eggs to opening frogs – it is basically the same behavior, using their specialized dentition.
One element that we did not get to discuss in detail, is that this adaptation leads to the exploitation of otherwise unattainable eggs such as those of sea turtles. Studies on Orchid Island, off the coast of Taiwan, showed that Taiwan Kukri Snakes (Oligodon formosanus) burrowed into the nests of Green Sea Turtles (Chelonia mydas), taking up temporary residence as they slit open and consumed the contents of egg after egg. Even more interesting, studies also show occurrences of territoriality among the nest-invading Oligodon. Male kukri snakes typically found and occupied the nests initially, but then females would arrive, and vigorously drive off their male counterparts, along with any latecomers. Territorial behaviors, while common among lizards, are poorly documented in snakes.
The Orchid Island story gets much more interesting and complex. Left to their own, a certain percentage of sea turtle eggs deposited in nests become part of terrestrial food webs, providing nutrients either though predation, mishap, or infertility, and along the way supporting a host of other organisms. Sea turtle nesting is a seasonal event, and when turtle eggs are not available, Oligodon prey on lizard eggs like those of the Sun Skink (Eutropis longicauda).
But wait, there’s more! Researchers discovered that female Sun Skinks on Orchid Island exhibited parental care by guarding their eggs. At the approach of a kukri snake, the skinks would violently attack the snakes, attempting to drive them off. In controlled studies, genetically identical sun skinks from mainland Taiwan exhibited no such parental care behavior. Researchers also found high numbers of Oligodon formosanus on the island, presumably sustained by seasonal influxes of sea turtle eggs; in turn these snakes may have put a lot of pressure on sun skink populations, triggering the adaptation of nest guarding behaviors. Lab testing has shown that the aggressive egg guarding behavior of the female sun skinks is successful at least part of the time.
It is also worth noting that in 2008, sea turtle conservation practices were put into practice on Orchid Island. The collection and off-site incubation of turtle eggs almost certainly impacted the nutrient stream and food webs on the island, including the kukri snakes and sun skinks, and serves as a cautionary example of the potential harm behind single-species conservation.
Batesian mimicry is another aspect of Oligodon that Justin, Alex, and I didn’t have time to discuss. Perhaps the most striking example involves the venomous Malayan Striped Coral Snake (Calliophis intestinalis) and the non-venomous Eight-striped Kukri Snake (Oligodon octolineatus). During my visit to Taiwan, the Oligodon ornatus I encountered lifted and coiled its tail so that the bright underside was visible (see photo above), perhaps mimicking a behavior that some of the venomous coralsnakes of southeast Asia are noted for.
Thanks for reading along, and thanks for listening to the show! As a bonus, here is the Mandarin Ratsnake I encountered in Taiwan, that we talked about in the episode! Also, see the related publications listed at the bottom. Feel free to request a PDF copy of any of them.
Related publications
Lee et al., 2025. Color polymorphism, taxonomic confusion and cryptic diversity in the kukri snake Oligodon albocinctus (Cantor, 1839) (Squamata: Colubridae). Zootaxa 5714(1)
Lee et al., 2024. A multi-gene phylogeny of the Asian kukri snakes (Oligodon Fitzinger, 1826): Sharpening the blade of the second largest serpent radiation (Reptilia: Squamata: Colubridae). Molecular Phylogenetics and Evolution 201 (2024) 108215
Lee et al., 2023. Kukri snakes Oligodon Fitzinger, 1826 of the Western Palearctic with the resurrection of Contia transcaspica Nikolsky, 1902 (Reptilia, Squamata, Colubridae). PeerJ 11:e15185 DOI 10.7717/peerj.15185
Lee, Justin L., 2022. First Record of the Annam Kukri Snake Oligodon annamensis Leviton, 1953 (Squamata: Colubridae) From Thailand. Tropical Natural History 22 (2022): 100-107
Lee et al., 2021. Rediscovery and distribution extension of the rare Kukri Snake, Oligodon hamptoni Boulenger, 1918 (Reptilia, Serpentes, Colubridae), with the first record of this species from China. Herpetozoa 34: 13–21
Pawangkhanant et al., 2024. A new species of karst-associated kukri snake (Reptilia: Squamata: Colubridae: Oligodon Fitzinger, 1826) from southern Thailand. Vertebrate Zoology 74, 2024, 359–379
Bringsøe et al., 2021. Gruesome twosome kukri rippers: Oligodon formosanus (Günther, 1872) and O. fasciolatus (Günther, 1864) eat Kaloula pulchra Gray, 1831 either by eviscerating or swallowing whole. Herpetozoa 34: 49–55 (2021)
Bringsøe et al., 2020. Eviscerated alive: Novel and macabre feeding strategy in Oligodon fasciolatus (Günther, 1864) eating organs of Duttaphrynus melanostictus (Schneider, 1799) in Thailand. Herpetozoa 33: 157–163 (2020)
Coleman, et al., 1993. Kinematics of Egg-eating by the Specialized Taiwan Snake Oligodon formosanus (Colubridae). Journal of Herpetology, Vol. 27, No. 3, pp. 320-32
Huang et al., 2011. Territorial behavior in Taiwanese kukrisnakes (Oligodon formosanus). PNAS vol 108, no 18 pp.7455–7459
Lin et al., 2023. Loss of sea turtle eggs drives the collapse of an insular reptile community. Science Advances 9, eadj7052 (2023).
Pike et al., 2016. Surf and turf: predation by egg-eating snakes has led to the evolution of parental care in a terrestrial lizard. Scientific Reports 6, 22207; doi: 10.1038/srep22207 (2016).
Mori et al., 1992. Unusual Putative Defensive Behavior in Oligodon formosanus (Serpentes: Colubridae): Head-slashing and Tail-striking. Journal of Herpetology Vol. 26, No.2, pp. 213-216.
Copyright 2026 Mike Pingleton. No pseudo-intelligences were used in producing this work. Please note that no part of this work may be used or reproduced in any manner for the purpose of training artificial intelligence technologies or systems. All rights reserved.
