Author: Claire Dufour

Communication is a prerequisite of human society. But when you look, smell and hear around, you rapidly realize that we are not the only ones to communicate. Indeed, plants, fungus, animals and other living things such as bacteria show extraordinary ways to “talk” to each other.

The diversity of animal signals  (e.g. visual, acoustic, chemical) and their evolution has particularly fascinated biologists for decades. Etymologically, the term “communication” implies to share information between a signaler and a receiver, but the interplay between the two remains extremely challenging to study, especially in animals in their natural environment.

The use of robots in ecology is in its infancy, but promises great advances in the study of animal communication. Lizards are not outdone with this robotic revolution (see previous AA posts and several others should be forthcoming!). The use of lizard robots allows researchers to control the signal stimulus directly in the field and to address questions related to species recognition, mate choice and evolution of aggressiveness, for instance.

In a recent paper, Dave Clark and collaborators went further by designing an interactive lizard robot! Yes, the study is about Galapagos lava lizards, but it deserves great attention in the Anole Annals community as understanding the processes underlying lizard communication is of pressing interest in anole research and the interactive robot may help to understand its evolution. The authors presented a bio-mimetic conspecific robot and tested whether an immediate or a postponed 30s response of the robot to the subject’s display influenced the display latency and duration of the focal individual. They found that immediate display response by the robot to a subject’s bobbing display stimulated the focal lizard to display more rapidly and more often than when the robot’s response was delayed. These results suggest that subjects perceived a rapid response from their robotic contestant as being more aggressive than a delayed response.

This study is the first interactive robot playback experiment with lizards in natural conditions and it demonstrates that the response ‘timing of the receiver is a crucial factor of lizard communication.

 

Reference:

Clark, D.L., Macedonia, J.M., Rowe, J.W., Austin, M.R, Centurione, I.M, Valle, C.A. (2019). Galápagos lava lizards (Microlophus bivittatus) respond dynamically to displays from interactive conspecific robots.  Behav Ecol Sociobiol 73: 136. https://doi.org/10.1007/s00265-019-2732-6

When you hear about a spa, you visualize a relaxing place where soft skin peeling is commonly practiced. Even if the place is human-specific, skin peeling itself has been recorded in the “animal world,” and in a way that goes beyond your imagination.  

Indeed, some species of scincid and gekkonid lizards are known to lose a part of their skin during drastic regional integumentary loss (Bauer et al., 1989, 1992a, 1993; Bauer & Russell, 1992). Such loss is dependent on the bilayering of the dermis and the inherent weakness of the outer layers of the skin and is used as an antipredator strategy (such as the tail autotomy), particularly during the early stages of subjugation by the predator (Bauer et al., 1989, 1992, 1993; Bauer & Russell, 1992). Nonetheless, this practice has severe costs related to radiation exposure (particularly in diurnal species), osmoregulation and immunological integrity (Bauer & Russell, 1992).    

Back to the Caribbean island of Dominica the past month, I sampled populations of Anolis cristatellus. During the routine measurement process on a big male, I was surprised to see that the lizard lost his entire skin as soon as I touched him, the muscle being nearly apparent (Fig. 1). I measured more than 2.000 anoles, and this guy was the first one to lose his skin in my hands. Did I sample a very special individual? The response is probably “no.” Within the same day, this regional integumentary loss occurred in two adult males and one adult female A. cristatellus in total. To my knowledge, such a skin loss was not observed in anoles before. Could it be an underestimated antipredator strategy in Anolis?  If yes, could it be different on island vs mainland species as suggested Bauer & Russell (1992) in gekkonid lizards? The anole world has not finished to surprise us! 

References:

Bauer, A.M.; Russell, A.P.; Shadwick, R.E. 1989. Mechanical properties and morphological correlates of fragile skin in gekkonid lizards. J. Exp. Biol. 145(79-102)

Bauer, A.M.; Russell, A.P.; Shadwick, R.E. 1992. Skin mechanics and morphology in Sphaerodactylus roosevelti (Reptilia: Gekkonidae). Herpetologica. 48(124-133)

Bauer, A.M.; Russell, A.P. 1992. The evolutionary significance of regional integumentary loss in island geckos: a complement to caudal autotomy. 4(343-358).

Bauer, A.M.; Russell, A.P.; Shadwick, R.E. 1993. Skin mechanics and morphology of two species of Pachydactylus (Reptilia: Gekkonidae). S. Afr. Tydskr Dierk. 28(192-197)

The anole dewlap is a powerful visual signal to attract sexual partners and repel rivals and predators. The diversity of dewlap color has fascinated researchers for decades, environmental lighting and species competition being among the potential drivers of its evolution. At the Evolution meeting in Montpellier, Winter Beckles, PhD student at the University of Miami,  presented his great study on the bark anole.  Anolis distichus invaded Miami through multiple introductions events. Intriguingly, these little lizards occupy a  range of habitats and present polymorphisms in their dewlap color within populations.

For his PhD, Winter and his colleagues measured the reflectance spectrum of the habitat and of the dewlap of 20 to 25 males per population. They found a strong positive correlation between the relative abundance of habitat UV light and the UV light reflected by the dewlaps. But that was before Hurricane Irma hit Miami in September 2017. And what a destruction it was: the trees, the canopy, the plants and by consequence the habitat lighting, were affected by this catastrophic event.

Despite the obvious negative consequences of the hurricane, this event gave a great opportunity to test the effect of extreme habitat change in the variability of dewlap color in the bark anole. Thus, after Irma, Winter and his colleagues immediately returned to each field site to collect reflectance data of the habitats and dewlaps: Irma altered the light profiles across sites and the correlation between dewlap and ambient light disappeared. In order to track how the relationship between dewlap color and habitat lighting develops over time, Winter plans to collect data in 2018: maybe the correlation will be back. Looking forward to seeing the paper.

Check the new episode of the series “Chris & Z’Andy, the 2 anoles in Dominica ” published in PeerJ (Dufour, Herrel & Losos 2018)!

See also episode 1

Game: find the snake (Elaphe sp) and the lizard (male Anolis sagrei)

Last April and May, I was in Florida… not for holiday but in order to discover the “lizard word” during a field session with Ambika Kamath. For her Ph.D. project in the Losos lab, we collected data on the spatial use of male and female Anolis sagrei to determine the reproductive system of this species. I was surprised when I realized how easy it is to observe these little guys directly in the field! I was really excited to see them mate, fight, display and eat: it was incredible! But the more impressive memory is when I saw a male A. sagrei being eaten by a baby rat snake. I wondered whether this was a really common sight… but I was told I was lucky that day!

The scene happened during a survey, when I saw this unmarked male displaying on a branch… but not on any tree: a tree occupied by a baby rat snake! It was thrilling to see the snake stalking the lizard in a sit-and-wait foraging strategy (as far as a snake can sit…). Even though five long minutes passed where the lizard had time to look around (photo 1), it still jumped on the very branch where the snake was waiting. A great occasion for the predator, who directly started to bite and wrap his body around the lizard whose helpless bites and dewlappings had no effect on the outcome of the fight (photo 2 & video).

After this, I wondered what the mechanisms of predatory detection and avoidance in lizards (including the tail loss ability) could be. Indeed, during predator-prey encounters, there is a transfer of information between them in the form of signals (e.g. auditory, chemical, visual) which may directly modify the outcome of the encounter. Anolis lizards possess a large and complex behavioral repertoire which consists mainly of visual signals (e.g. dewlapping, push-up, head-bobbing) that are used during social interaction, but also in encounters with a predator.

Leal and Rodriguez-Robles in 1997 showed that Anolis cristatellus may rely more on behavioral signals than on flight to avoid predation. It is indeed what I saw: the male lizard displayed to the predator… But I still wonder why this little guy suddenly jumped directly on the snake! Is it possible that he displayed to me and that in front of two potential “predators,” the lizard focused only on the first (or biggest) one that he saw? Apparently, this lizard was more afraid of me than of the snake… wrong choice, I was not going to eat him!

Then, the last day of my field work, I also saw a female cardinal with a big A. sagrei male in her beak… really strange… but I think that the “lizard world” has not finished to surprise me!

Leal, M. & Rodriguez-Robles, J. (1997). Signalling displays during predator-prey interactions in a Puerto Rican anole, Anolis cristatellus. Animal Behaviour 54(5), 1147–54. doi:10.1006/anbe.1997.0572