How adder-like is Echiopsis curta?

Comparison of snakes in similar ecosystems in southwestern Australia and the southwestern Cape of South Africa.

The Barrensncf Caledon coast.

Echiopsis curta (https://www.inaturalist.org/taxa/35270-Echiopsis-curta) is an elapid, related to Notechis. Itnis the closest counterpart for the viperid, Bitis armata (https://www.inaturalist.org/taxa/95801-Bitis-armata).

Both are southern endemics within their continent, temperate, oligotrophic, heathland, and commonn in the ecosystems studied.

They have the same size and shape: mean length about 40 cm, maximum length 60 cm.

Their head sizes and shapes are similar, and they share vertical slit pupils, pale upper irises, and oblique whitish markings on the upper lips or jowls.

Neither has a caudal lure.

Both are slightly polychromatic, and rely mainly on camouflage.

Both are venomous, sufficient to kill a small mouse within 5 minutes, and front-fanged, and hunt by ambush on the ground without submergence.

Both are fairly catholic in diet (amphibians, lizards, and some small mammals and even birds), with a bias for frogs (Shine).

Both hang on to small prey, but release large prey and follow it to its place of expiry, being incapable of rapid locomotion or constriction.

Both are viviparous, bearing 4-9 (maximum 14-15) offspring in late summer or autumn.

Both have neonates 11-14.5? cm (check for E. curta).

Both emerge in dim light and under cool conditions.

The differences between them are their defences against their own predators.

Echiopsis curta is adder-like in being unusually irascible if provoked, with relatively ling fangs? and potent venom for an Australian elapid of its size, and to this extent is convergent with Bitis in much the same way as the Australkan elapid Acanthophis (Shine).

However, E. curta is far less elaborately camouflaged than B. armata, has a much less indurated skin. The adder has hard, keeled scales, despite having more, not fewer, scale rows than its Australian counterpart.

Echiopsis curta hardly hisses, even when touched (check), whereas B. armata makes anninsistent,mpuffing sound when a potential predatorsddraws near, and before contact is made.

The exact difference in fang length, position, and mobility, and venom-delkverynsystems, are unknown.

This seems to be a classic case if two Good counterparts in habitat, morphology, and foraging ecology, and reproductive behaviour.

They differ simply because of the very different incidences of vertebrate predators in their habitats.

Note that the response of these forms is in terms of greater protectiveness of the adult, not greater numbers of offspring per birth.

A second adder-like elapid occurs at the Barrens, albeit rarely: Acanthophis antarcticus (https://www.inaturalist.org/taxa/35060-Acanthophis-antarcticus and https://www.australianreptileguide.com/common_death_adder and http://www.reptilesofaustralia.com/snakes/elapids/aantarctic.htm). This more resembles Bitis cornuta, whixh does not reach the Caledon coast.

The theme of lesser defensiveness and greater body size (without lesser litter size) in Australia than southern Africa is epitomised by Notechis scutatus (the Barrens) and Hemachatus haemachatus (Caledon coast).

Both are substantial ()> 1 m long and moderately stocky), viviparous elapids, incapable of rapid pursuit of prey, or rapid escape from their own predators.

Both N scutatus and H. haemachatus have anbhntidy banded pattern, as suited to warnjng an jntruder if a seriously venomojs snake as to camouflage. Both have pale, bright ventrolateral surfaces, conspicuous when the snake moves in alarm.

They often eat large, slow-moving amphibians, while accepting a wide variety of vertebrate prey, and are neither particularlynsecretive bybdaylight nor strictly nocturnal.

Their moist, grassy/sedgey, relatively productive environments support relatively many and diverse predators willing to tackle a cinspi uous, medium-size snake.

These factors may explain why these snakes are among the most dramatically defensive reptiles at the Barrens and the Caledon coast.

Posted on November 2, 2023 10:26 AM by milewski