Aaaand, we’re back! This time around I was able to play around with manipulating physical (size) and genetic (relatedness) variables between aggressive cannibal tadpoles (the infamous Dendrobates tinctorius) in collaboration with Lutz Fromhage, Janne Valkonen, and Bibiana Rojas.
The D R A M A is for real. . . it turns out that both size and relatedness play a role in driving aggression between tadpoles, where individuals are more aggressive towards a counterpart with increased size asymmetries and decreased genetic relatedness. In other words, large non-siblings are significantly more aggressive than large siblings (exhibiting almost twice the amount of aggressive behaviors).
But it doesn’t stop there.
The most fascinating thing (IMO) is the shift in latency to aggression depending on relatedness. We find that there is inversion in biting behavior as size differences increases, where sibling pairs with large size differences attack significantly faster than non-siblings. Thus, although large siblings were less aggressive overall, they had a shorter latency to aggression in dyads with large size differences.
Is that not simply fascinating? Why are siblings who are quite disproportionate in size demonstrating aggressive behavior so quickly? Perhaps that biting is not simply an aggressive behavior, but a means for identification and the assessment of relatedness? Or perhaps it is a behavioral response to establish dominance within a pair?
No matter how you slice it, there is something going on in their little tadpole brains where individual behavior is different when faced with non-related or related individuals. From this clear kin discrimination and really cool cognition work headed by Fischer (2020), we believe that there is kin recognition in Dendrobates tinctorius. To read more about the details of our study and learn about aggression in cannibals, check out our pre-print!
When we observe animals, be it in the jungle, under water, or even in your own back yard, we learn to recognize individuals over time. Maybe you know your neighbourhood squirrel because it has a ripped ear, or you notice a butterfly because it has a unique pattern. This process, the act of distinguishing individuals, is fundamental in behavioral research.
But what do you do when all of your individuals within a population look similar?
In this study, I attempted (along with one of my best friends, Guillermo Garcia-Costoya and my advisor Bibiana Rojas) to tag young poison frog tadpoles with fluorescent elastomer tags. This is especially interesting because, to date, tropical larval amphibians had never been tagged; further, we marked the smallest and youngest amphibious animal ever recorded.
Now you see me, now you don’t:
When tracking tags across development we find that the probability of retention and observation differ across time. This means that just because someone didn’t observe the tag doesn’t mean that the tag is actually lost. This is important to take into account when working with mark-recapture studies.
What’s so cool about elastomers is that they’re small and durable. We now have work showing that we can tag tiny little tadpoles (before they have cool back patterns or are transported by their fathers!) and find out where they are carried or even how tadpole communities change over time in small water holdings. This methodology will hopefully be of use to future biologists who working in conservation or on behavior in the tropics.
Animals can sometimes be downright bizarre. We, as biologists, still don’t quite understand why animals behave the way they do, but every day we get a little bit closer to a more complete reality of the natural world that we observe. One of the most fascinating behaviors I have ever watched is that of cannibalism, where an individual kills and then consumes part or whole of another individual of the same species. And although it’s weird, it’s not rare at all; in fact, it’s present in every animal clade alive on Earth today! Mothers eat their babies, fathers feed their babies to other babies, babies eat each other. . . the carnage is truly ubiquitous.
Feel free to download our quick guide to cannibalism– but watch out! It’s a slippery slope to becoming fascinated with this deliciously intriguing behavior 😉