Territoriality: Attempting a One-Two Punch

In my major Ph.D. project, I questioned the idea that territoriality is a good or useful description of Anolis lizards’ mating systems. When I began working on this question, I planned to primarily use an empirical approach, measuring the movement patterns and mating patterns of a population of Anolis sagrei in a way that didn’t depend on territoriality. But anticipating future criticism, I realised that because I’d be working in one population of one species, my empirical work could readily and reasonably be dismissed as an aberration without a broader foundation on which to place it.

This realization led to the historical review in which my Ph.D. advisor Jonathan Losos and I examined the history of research on Anolis territoriality. I’ve written about this historical research quite a bit before, but haven’t said much about the empirical work, leaving the two complementary halves of this project unintegrated. That’s partly been because the empirical work wasn’t published until recently. But it’s also because in contextualizing the problem tackled by the empirical paper, I have to basically recount the whole of the historical review. There really hasn’t been room to talk about both in a single venue, and there still isn’t, but I’m going to tell you a bit more about the empirical paper to balance things out. You’ve heard a little about it before–I wrote field notes about one of the males in this study (interesting addendum: U131 fathered none of the offspring of the females he encountered!) and about a tiny survey of green anoles that we conducted concurrently.

The empirical paper is now published, in the Proceedings of the Royal Society B! Here’s an awesome press release about the study from UCSB that will give you the gist of it, but in short what we did was:

  • Catch and mark almost every lizard we saw, and then measure the spatial locations of as many lizards as we could by repeatedly surveying as big an area as we could.
  • Make a map of all the trees within our sampling area.
  • Measure the body size and estimate the population-level growth rate of males
  • Collect a subset of the females, bring them into the lab, and collect the DNA of their offspring.
  • Devise a mathematical approach to estimating encounters between males and females from data on their spatial locations. Combined this with the growth-rate estimate to calculate the size of males at their encounters with females.
  • Use DNA sequencing to figure out the likely fathers of the females’ offspring; we leaned on the estimates of male-female encounters to do so.
  • Use a clever and (I think!) pretty original approach to quantifying sexual selection on body size and movement patterns by comparing the traits of males that encountered females to the traits of the subset of those males that actually fathered offspring.

In sum what we found was that male and female movement patterns spanned larger areas and were more dynamic than many of us had previously imagined, that females encounter multiple potential mates, that at least 60% and possibly up to 80% of females  mate with multiple males, and that sexual selection acts on male body size as well as males’ spatial extent and the timing of male-female encounters. I’ll let you read the press release and the paper itself to learn more about what we found (here it is on BioRxiv, essentially the same paper but freely accessible)!

Viewed together, I hope the historical and empirical papers make a convincing case that we’ve been looking at Anolis mating systems in a limited way for a long time, and that other, newer ways of quantifying mating systems in ways that don’t depend on territoriality can yield both interesting and sensible results. I see this work as opening up an arena of questions, both in Anolis and in other taxa where mating systems have been described in a static way for a long period of time.

I’m very proud of this paper. I remember a phase of grad school when I found it impossible to convince people that this work would turn out interesting, or maybe it was just that my own self-doubt prevented me from seeing others’ interest and support for this research. It remains true that this is one study of one population of one species, and it may well be that I turn out to be all wrong. Perhaps new explorations of Anolis mating systems will eventually lead us back to territoriality. But even if that’s the case, I feel confident that, thanks to this work, we’ll be able to approach that or any description of Anolis mating systems with clearer, more skeptical, and more discerning eyes.

This won’t be the last you’ll be hearing from me on this subject of lizard mating systems; for one, there are responses to our historical review that are in the process of being published, and we’ll have a chance to respond to them. I’m very excited to engage in an actual scientific dispute, and will do my best to do so respectfully and productively, especially since I have on-the-record views about what makes such disputes annoying. But in terms of research, I seem to be heading in other directions, which I think will be related to this work but maybe not directly. So I wanted to make sure that I put down here, all in one place, what I see this project as and what I hope it will achieve. Let me know what you think!

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One of our marked lizards for this study. Photo by Jon Suh.

What Should We Do With Natural History Observations?

With the nostalgia that invariably accompanies year-endings, I’ve been looking over my writing in 2015, trying to pick out the pieces I like best. My personal favourite, by a long distance, is this post I wrote for Anole Annals, titled “Are Brown Anoles in Florida Really Driving Green Anoles to Extinction?” Here’s the first paragraph, just to give you a sense of what it’s about:

Tell almost anyone in Florida that you’re doing research on brown anoles (Anolis sagrei), and they’ll express some distaste for your study organism. “I don’t like them,” they’ll say, “they’re invasive. Aren’t they driving the native green anoles extinct?”* Everyone—literally everyone who has lived in Florida for a whilewill tell you how their backyards used to be full of green anoles (Anolis carolinensis). Today, they report, these green anoles have disappeared and been replaced by the invading browns.

Green anoles are increasingly elusive in Florida.
Green anoles are increasingly elusive in Florida.

The rest of the post goes on to discuss why these “backyard tales” may be unfounded. The main takeaway of the post is that, rather than going extinct, it is possible that green anoles have simply shifted upwards out of sight in many habitats where they co-occur with brown anoles. I present some data from an informal, small-scale mark-recapture study we conducted in 2015, and make inferences from both the number and the sex ratio of the green anoles we caught to suggest that the green anoles in that site, and likely elsewhere, are still around.

Why do I like this post so much? Because it combines data and logic and story telling to challenge a rather prevalent notion, namely the “usual alarmist hysteria [about] green anoles being pushed to extinction” by brown anoles. Because it was born from observing animals in their natural habitats. Because it spurred comments from biologists and non-biologists, plus an accompanying post from Jonathan Losos adding an evolutionary dimension to the argument that green and brown anoles can coexist. But most of all, I like the post because it appears in the one location where people who are interested in this question are most likely to find it—a blog dedicated to the biology of Anolis lizards, a blog that is followed by a large number of professional and amateur Anolis enthusiasts.

That got me thinking about the best thing to do with datasets like the one I wrote about. Could it have been published as a short note in a natural history journal? Possibly, but only after much more effort from me into manuscript preparation and formatting, and months in review, demanding further effort from editors and reviewers. Does a study this small, this tentative, need peer review? Not really, and when published in a place like Anole Annals, readers are free to post comments clarifying or criticizing the methodology and conclusions. Would its reach have been wider, its impact stronger, as a published paper? Almost certainly not. Whether a blog post or a paper, people will reach it via a Google Search. Does any of this make these data inconsequential? No. I know my post is very far from earth-shattering, but it’s a thought-provoking dataset to people who care about Anolis lizards, and in it’s current location and format, it reaches those people efficiently. Of course, Anole Annals didn’t emerge overnight—I know that it’s taken time and effort from many contributers to establish and run—but I suspect that effort pays high dividends.

As a natural history enthusiast, I love the possibilities that a blog like Anole Annals affords for changing how we go about collecting and disseminating the natural history observations that field biologists accrue. But anoles are a special beast—most genera of organisms do not have such an ardent following. Can this model be scaled upwards in any way? I wondered aloud about this on Twitter a while ago, and the consensus was that the Encyclopaedia of Life, or something like it, was our best bet (thanks to Felicity Muth for the suggestion!)

I don’t think I’m suggesting that we do away with natural history journals entirely, because there is certainly a need for more comprehensive and substantial natural history research, for which publication in a journal (and the associated credit it brings) makes sense. But I know that many of us field biologists have far more observations and datasets that don’t get submitted as papers to natural history journals. It seems a shame not to share these at all—if and when I stop studying lizards, I know I’ll miss the chance to talk about my study organisms’ natural history at a venue like Anole Annals.

*Fun aside: the quote isn’t made up; it’s from a conversation with the talented tattoo artist, Rich Mal, from Anthem Tattoo in Gainesville. I recommend that establishment highly, in case you’re interested.

A Week in the Life of U131

When you’re collecting data on the behaviour of individual animals over time, as I am this summer, your observations sometimes feel less like a collection of numbers and more like a collection of personal narratives. Of course, the data are both numbers and narratives, and when it comes time to analyze this collection of datapoints and understand the patterns that emerge from it, the numbers will be all that matter. But in the meanwhile, before I can look the bigger picture, I enjoy considering the individual narratives. And this week, I encountered a lizard whose story illustrates why it’s worth considering these narratives at all.

I first saw U131 last Wednesday, a full two weeks into sampling at my current fieldsite on the University of Florida campus. He appeared on a perch near the edge of the park, which borders a patch of forest. I’m not sure how far he travelled to get to this perch, but within the next day he had travelled a further fifteen metres to arrive at the weirdest section of my fieldsite.

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These two logs and three tree trunks have housed at least fifteen different lizards over the last three weeks, including some of the largest males in the site. Why is this weird? It’s weird because the males in this area have shown no sign of excluding one another from the space around them—in other words, they aren’t being territorial. Still, I was skeptical that this already-crowded area could sustain yet another lizard. After all, lizards aren’t supposed to live in the reptilian equivalent of hippie communes.

But U131 seemed determined to grab a spot here. On Thursday, I spotted him locked in fierce battle with U36, a longtime resident of the logs. U36 has the red beads sewn into his tail, while the blur of yellow and black are the beads on U131’s tail.

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An hour later, they were still fighting, and it looked like U131 was getting the worse of it.

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The fight could have gone either way. While U131 is bigger than U36, which is almost always an advantage in an anole fight, U36 had the advantage of fighting on his home turf. I wasn’t too surprised when I saw, the next day, that U131 had wandered onward to a tree over 30 metres away.

DSCN0168But the logs must hold some allure, because by this afternoon, U131 had made the long journey back, and was busy displaying at another one of the area’s residents.

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We’ll see, over the coming months, whether U131 hangs on at the logs or moves elsewhere in the site to encounter and interact with other lizards. By the end of the season, U131 will be just one datapoint among hundreds, an example of a large male who didn’t maintain a territory across the whole breeding season. We’ll know by then if his behaviour is the exception or the norm.

But for now, U131 exemplifies the importance of the individual example. While the aggregate of all the lizards we observe will show us what does happen, a single lizard shows us what can happen. We now know, thanks to just a week of watching U131, that large male brown anoles sometimes move among perches many metres from each other, wandering in a way that we do not expect from territorial lizards. Whether signal or noise, U131’s narrative expands what we know is possible in the world of the brown anole.

A Macabre Start to My Time in Florida

I’m in Gainesville for what I’m anticipating will be my last Ph.D. field season. I’m here to study the movement patterns of brown anoles (Anolis sagrei), trying to understand how their behaviour departs from territoriality to allow for female multiple mating. One of my goals is to observe lizards over a longer period of time than most previous work on anole territorial behaviour, which is why I’m here so early.

But Florida saw an unusual cold spell last week, and it’s still a bit too cold for widespread lizard activity. This morning I saw some evidence that the lizards venturing out in this weather may not be making the wisest of decisions.

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I’m not quite certain how this brown anole died, but he did have just a single wound in his abdomen, from which his innards seemed to be spilling out. Maybe pecked by a bird or clawed by a cat (but then why didn’t he get eaten?)? Maybe accidentally squished by a person? Whatever the cause of his demise, this lizard probably couldn’t escape from it quickly enough. I’m not sure if this is a good or a bad omen for the rest of the season, but it’s an interesting one.

It’s worth noting that this is the first time I’ve seen a dead brown anole. Last summer in Gainesville, however, my field assistants and I saw several dead green anoles (Anolis carolinensis), none of whose causes of death were easily discernable. Here are a couple:

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