Varanus salvator in the Lumpini Park in Bangkok

Picture - Varanus salvator Michael Stanner E-mail: malpolon2000@yahoo.com Dear friends I am writing this message in an internet cafe in Khon Kaen. In a few days I shall be back in the Surin Rajabhat University (SRRU), and later on - in Bangkok and finally back in Israel. Michael Stanner E-mail: malpolon2000@yahoo.com Several days ago I was fortunate to have a unique (so I think) observation on the feeding behavior of Varanus salvator in the Lumpini Park in Bangkok. The monitor (ca. 140 cm total length + probably another 10 cm of missing tail-tip) was engaged in eating a ca. 40 cm suckermouth catfish (see below). Picture - Suckermouth catfish I always thought that just like snakes, monitor lizards always swallow their prey wholly, and for that purpose they are also equipped with cranial-kinetic capabilities - less developed than in snakes, but more developed than in other lizards. At first the monitor tore a hole in the skin and bore its head into the body like a vulture eating softer inner parts. Then it ripped the body with its jaws using its forefeet for assistance, eating smaller chunks of meat at a time - just like mammalian carnivores. After that it succeeded in severing the vertebrae column and separated the hind part of the body (ca. 10 cm + the tail fin) and swallowed it wholly in an anterior-posterior orientation in less than one minute. All in all, it was quite impressive - I don't think that I could cut off the hind part of the body without an ax or a big knife. What was left of the fish at the end of the meal was most of the head, especially the dorsal part of it that is particularly hard and covered with bony shields, and about 10 cm of the anterior spinal cord that remained attached to the head. After that the monitor left the fish, defecated and started with a typical varanid foraging behavior activity for ca. 5 min eating smaller chunks of meat and other leftovers that were scattered in the immediate vicinity, and then dived into the Khlong (water canal) and disappeared in the water. The observation lasted more than an hour and I carried it out from a distance of 3-4 m. The monitor usually ignored me completely, nevertheless it seemed that my presence did create a minor disturbance - once in a while it stopped eating and observed me and the surroundings motionless for 5-30 sec, and then resumed eating. Twice it moved 3-5 m away from me trying to continue with the eating activity behind vegetation and a fence. I recorded all the details in my notebook, as well as took several pictures and short videos. In terms of varanid feeding behavior, it was indeed a very interesting and enlightening observation, and that in spite of the fact that it is well known that Varanus komodoensis occasionally preys on domestic and feral cattle and water buffaloes that obviously cannot be swallowed wholly, but I have always tended to treat Varanus komodoensis as a category of its own somewhat detached from other varanids. I have never seen such a behavior in Varanus griseus, but I can't rule it out. Morphologically I see no reason why Varanus griseus (or other medium-sized varanids that are strong enough) would not use such prey-handling techniques. In that respect, if I remember correctly, unlike snakes whose teeth are posteriorily curved, conical and round in transverse-section, hence - adapted only for holding the prey in place and preventing it from sliding out of the mouth during the process of swallowing, Varanus teeth are laterally compressed and serrated, hence - adapted also for cutting and tearing off pieces of the prey. After my return to Israel I intend to check it out again, either in the literature and/or under the binocular. Later on that day I learned that the fish was a suckermouth catfish - probably Hypostomus plecostomus, but I am still not sure of the exact identification because there might be more than one species in Thailand. Suckermouth catfish is actually an introduced omnivorous fish from South America that causes havoc in local Thai ecosystems. It was introduced to Thailand as a cleaning (janitor) fish for aquaria for easing the lives of aquarium owners and sparing them the nuisance involved in cleaning the aquarium. When the fish grew and became too big they released it in local fresh water ecosystems (water canals, ponds, swamps, rivers, etc.) and in a few years it succeeded to spread all over Thailand eating fish-eggs (including eggs of commercially-important fish). Surprisingly, Thais that will readily eat anything that moves, don't eat suckermouth catfish claiming that its flesh is not tasty. If that's so, it is even more interesting, because (as you already know) Varanus salvator, which is by far the most loathed animal in Thailand may now have a chance to change its negative image, become the main biological controller of suckermouth catfish, and thus - become the saver of the Thai fresh-water ecosystems. All the best and cheers - Michael. P.S. If you conclude from my emails that I have a lot of free time, you are right - never had so much of it. Picture - Suckermouth Catfish Picture - Suckermouth Catfish