Varanus Yuwonoi (V. yuwonoi)
The black-backed mangrove monitor was only observed around the villages of Akesahu and Kao, both in the western part of Teluk Kao (Kao Bay) on Halmahera. The type series was collected near Jailolo (Harvey and Barker, 1998). Interviews with locals and animal dealers suggest that this species is widespread throughout the island. Eyewitness accounts of Varanus yuwonoi like animals from Morotai, Bacan, and even Obi exist, but still need confirmation.
Varanus yuwonoi is a difficult species to study. Despite frequent observations by local hunters, specimens are very rarely encountered out in the open. Considering the difference in size, which is presumably also reflected in trophic level, this species probably does not reach population densities as high as Varanus caerulivirens. A less active mode of hunting (sit and wait/ambush) may also result in the fewer encounters with V. yuwonoi.
|Varanus Yuwonoi-V. Yuwonoi|
Traps used by locals specifically for this species are always set up around megapode bird (scrubfowl) nests in
inland forests. The unusual pigmentation of the tail, body and neck breaks up the silhouette of the animal very well as they lie on the forest floor. Considering that the smaller and more predator-vulnerable species in the Moluccas have not evolved such an elaborate camouflage, it may have evolved rather as a means to escape detection from potential prey. The head is comparatively powerfully built and the teeth proportionately longer than any of its close relatives, even in comparison to most other more distantly related varanids.
Considering these facts, the author hypothesizes that Varanus yuwonoi is an ambush predator, favoring sites in the forest such as megapode nests, that are frequented by a variety of potential prey items. It is uncertain whether large individuals can kill adult scrubfowl, but the large nest mounds attract a number of smaller birds such as pigeons, and also lizards, snakes, and invertebrates, as well as the frequently hatching megapode chicks. According to local people, this species is also occasionally seen digging into these nests in search of eggs.
Additionally, observations of intraspecific aggression within the Varanus yuwonoi and Varanus doreanus clade (Ast, 2001) in captivity would support a hypothesis that V. yuwonoi could be an ambush predator. With few exceptions (Sweet, 1999, 2007), widely foraging monitor (and other scleroglossan lizards) species are not territorial; however, the two species (Varanus scalaris and Varanus glebopalma) known to be territorial are both ambush hunters. For a sit and wait predator favoring prey “hotspots”, a certain degree of territoriality could be expected to evolve. The largest individual measured 146 cm in total length; this specimen however did not appear to be fully grown, and according to locals they occasionally grow much larger.