Here are some amazing things that me and my friends have been talking about lately. They all concern fascinating discoveries or insights into unusual aspects of tetrapod behaviour.

We'll start with my current obsession: the short bit of underwater footage (16 seconds long) that shows an adult Lowland tapir Tapirus terrestris 'walking' (at great speed) along the bottom of a lake or river. The books say that tapirs do this (e.g., "This species is known regularly to walk on river beds"; Downer 2001, p. 474), but I'm thinking that this is the first time it's ever been filmed. I've watched the footage on facebook (Vladimir Dinets brought it to my attention) but haven't yet seen it elsewhere online. Best I can do, then, is provide this screengrab...

"Tapirs sometimes walk on the bottom of lakes and rivers". Oh really? Yes, really.

Here's another weird aspect of behaviour recently captured on film: sidewinding behaviour in a Green anaconda Eunectes murinus! Sidewinding has always been regarded as an adaptation for movement on shifting or loose substrate, and a form of locomotion only seen in small snakes (those less than 1 m long). Until now. As described by Ryerson & Horwitz (2014), a Green anaconda 2.75 m long was filmed (actually, way back in 2011) engaging in sidewinding - the first report of this behaviour in a large snake.

Sidewinding Green anaconda: this is a screengrab from Bill Ryerson's footage (available on youtube and easy to find).

As you can see from the video footage itself (thanks to Owen Davies for alerting me to its existence), the snake is quick, moving much faster than is possible using rectilinear locomotion and the other forms of movement usually associated with boas and pythons. It's also doing its sidewinding on grass and compacted soil, not on a "shifting or loose substrate".

Diagram (from Doody et al. 2014) of Yellow-spotted monitor nest burrow. The nest chamber was c. 1.6 m beneath ground, the spiralling burrow that led to it being filled with soft, moist soil.

And, still on the subject of squamates, have you seen Doody et al.'s (2014) amazing paper 'Cryptic and complex nesting in the Yellow-spotted monitor, Varanus panoptes'?

I've written about varanids and their behavioural complexity on a few previous occasions (see links below), but this study is so neat it can't be ignored. It turns out that Yellow-spotted monitors (also called Argus monitors) construct complex warrens, with the individual spiralling burrows within the warren system being (probably) the most complex structures constructed by any (non-bird) reptile. There's more to come on this discovery in future and I'll be blogging about it again when the time is right...

Aerial self-righting behaviour in a Chukar chick. Image by Dennis Evangelista.

Finally, a quick thing on birds. We're all familiar with the 'aerial righting' behaviour of cats. Throw one out of a window and it (usually) twists and manages to land on its feet. Is this sort of thing present in birds as well? If it is, it's of great interest as goes ideas about the origins of flight behaviour, since self-righting - as a means of preventing death or injury following falling - could have been involved in the evolution of flight behaviour and flight surfaces. Evangelista et al. (2014) dropped Chukar Alectoris chukar chicks (some of the birds were dropped in an upside-down position) and found that, via asymmetrical flapping and leg movement, the birds were often able to successfully self-right, even at just 1 day old (post-hatching). After 9 days of age (post-hatching) they switched to symmetrical wing movement. What's notable is that this self-righting use of the wings was used before other juvenile behaviours associated with partly-developed wings, like wing-assisted incline running (WAIR). The possibility being hinted at here is that use of partially developed wings as self-righting aids might have had a crucial early role in wing evolution.

What else is neat and new? Let me know what's been capturing your attention in the comments below; you know you want to.

For previous Tet Zoo articles relevant to some of the topics covered here, see...

Refs - -

Doody, J. S., James H., Ellis, R., Gibson, N., Raven, M., Mahony, S., Hamilton, D. G., Rhind, D., Clulow, S. & McHenry, C. R. 2014. Cryptic and complex nesting in the Yellow-spotted monitor, Varanus panoptes. Journal of Herpetology 48, 363-370.

Downer, C. C. 2001. Tapirs. In Macdonald, D. (ed) The New Encyclopedia of Mammals. Oxford University Press, pp. 474-475.

Evangelista, D., Cam, S., Huynh, T., Krivitskiy, I. & Dudley, R. 2014. Ontogeny of aerial righting and wingflapping in juvenile birds. birds. Biology Letters 10: 20140497.

Ryerson, W. G. & Horwitz, S. 2014. Eunectes murinus (Green anaconda). Behavior/sidewinding. Herpetological Revew 45, 337-338.