From matte banded to glossy black: structures underlying colour change in the caudal lures of southern death adders (Acanthophis antarcticus,Reptilia: Elapidae)

Abstract

Many ambush-foraging snakes move their tails to entice prey within striking range (‘caudal luring’). During ontogeny, the conspicuous hues of caudal lures change to match the cryptic patterning of the body/head. This coincides with decreased luring behaviour and reflects the trade-off between prey acquisition and camouflage as the snake grows. Australo-Papuan death adders (Acanthophis, Elapidae) are unique in that both juveniles and adults use caudal luring, but ontogenetic colour change has not been investigated. We examined the spectral reflectance, microstructure and pigmentation of caudal skin in wild-sourced and captive bred Acanthopihs antarcticus ranging in body size (snout-vent length 116–674 mm; mass 3–832 g; N = 33) to test whether colour properties change as snakes grow. We found that lure colour is distinct from the cryptic body skin across the life history, and changes from a matte banding pattern (grey/black) in neonates/juveniles, to uniform and glossy black with a yellow ventral stripe in larger snakes. These colour changes are caused by increases in dermal pigmentation and a transition to a smooth, interlocking epidermal microstructure. To understand the selection pressures that might be driving ontogenetic colour change in this species, further studies should test how different prey types respond to distinct lure morphologies.

Habitat determines convergent evolution of cephalic horns in vipers

“…Ambush foraging has also been observed in the horned sea snake, Hydrophis peronii Duméril, 1853 (Elapidae; Borsa, 2008). Acanthophis (Elapidae), in which some species have horn-like supraocular scales, share remarkable morphological convergence with terrestrial vipers and like many vipers also employ caudal luring to attract prey (Shine, Spencer, & Keogh, 2014;Crowe-Riddell et al, 2021). These comparisons may support the hypothesis that horns evolved under selection for crypsis in ambush foraging snakes.…”

Tail movements by late-term fetal pitvipers resemble caudal luring: prenatal development of an ambush predatory behaviour

“…Schuett 2015, personal observation). Caudal luring occurs in other viperid taxa [32][33][34][35][36][37] and in several other snake lineages [31,39,41]. Because snakes are extremely sensitive to air-and substrate-borne vibrations [42][43][44], it is possible that handling and use of ultrasonography incited the tail movements we have described; few studies have investigated motivation or stimulus control in caudal luring [26,31,45].…”

“…Caudal luring is a category of luring mimicry (commonly termed aggressive mimicry) often employed by newborn and juvenile snakes [ 26 , 27 , 29 ], and is most prevalent in viperids [ 26 , 29 – 37 ] but is present in several other snake lineages [ 38 , 39 ]. Our findings in this paper are significant for at least two main reasons.…”