16 September 2012

Highlights of Field Season 4: The Final Release

Good evening lizard-lovers,
I hope you enjoyed the last post in which I got a little off-topic of summing up the field season with a tonne of baby pictures...
Anyway, this time I promise to actually write a concluding blog this time.

First off, as I may or may not have mentioned before, we decided to exclusively catch S. undulatus this time. The reasoning behind this was mainly that mark-recapture of the sort that measures natural selection requires one initial capture, and at least two more recaptures following. We already have this completed for H. maculata... May/June 2011, August 2012, and May/June 2012. Because we decided to add the second species, S. undulatus, May/June of this year we decided to focus on them this season (July/August) because we had under a month and needed to increase our sample size... (yes this also means we'll be going back next spring for our last recapture!)

Well, unfortunately, recapture-rates (from lizards marked in the spring of this year) weren't nearly as good as they were for H. maculata.

       The release of a little S. undulatus that certainly
got going as soon as we let him go!

Overall, of the over-200 lizards we caught, only ~10% showed elastomer marks from the spring. This is surprising since after the summer last year, we had a 60% recapture rate for H. maculata. We can think of two possible reasons behind this low recapture rate. The first is that perhaps the elastomer tags are falling out. Perhaps I am not tagging the lizards deep enough and they are shedding their tags with their skin. We thing this is unlikely because we'd see a number of lizards with some, but not all of their tags remaining- i.e. the ones that were not deep enough. This doesn't seem to be the case... either lizards had tags, or they didn't. We hope that with all the photographs, scans, and gps coordinates we took, we can match up the lizards determine if they really did lose their tags.

Our "field schedule" including person-hours, lizards-captured, and some other... interesting drawings that show up after four people have been living in close proximity for far too long.
Of course, it is also possible that the population size of S. undulatus is much larger than we had anticipated (this is what mark-recapture calculations should tell us)... and this species is far more elusive. Considering what we know about the fence lizards... they do seem to be elusive. They are more arboreal than the lesser-earless lizards, and hide extremely well in vegetation (such that we often have to wait for an hour for the little fellows to re-emerge).

Sometimes we mistake this species, the side-blotched lizard (Uta stansburiana) for S. undulatus when it flashes by through a bush. These little ones are only found on the very edge of White Sands... often only the first dune off the dark soil desert. As of yet, it's a mystery why the side-blotched lizard hasn't colonized and adapted to White Sands.
Regardless of the extra patience it required to catch S. undulatus and the lower recapture rate, the field season was a great success with an average of 13 lizards per day. We even got a chance to head over to the Jornata Long Term Ecological Research Site (one of our dark-soils sites) and take a look at some of the species there:

One of the cutest/fattest lizards of all- a Texas horned lizard (Phrynosoma cornutum)

Lizard food? Unlikely... in all the lizard guts I've dissected.. I've never seen evidence of them having eaten an Anisoptera.
Recognize this little guy? My supervisor likes to call them the "junk lizard" of the desert. I took this action shot just after we let this one go... 
Well with that I will finally sign off for this year. Hopefully soon I will be able to post some results regarding the direction and magnitude of natural selection on the two White Sands lizard species- the lesser-earless lizard (Holbrookia maculata) and the Eastern-fence lizard (Sceloporus undulatus). Is natural selection still acting? What form does it take? Is it similar in both species? What about the population dynamics? Is there a fifty-fifty sex ratio? What is juvenile recruitment? How far do lizards disperse and do both species overlap in habitat use?
So many questions... only one dissertation (for now!)

Thank you everyone for following! Thank you to my great field assistants (Jackie Howells, Isaiah Hoyer, and Michaela Brinkmeyer), and especially the lizards for their reluctant participation in the noosing, prodding, flattening, and injecting that is my project!
Until next time, good night herps and herpetologists of the world!
-S. Des Roches

Highlights of Field Season 4: White Sands the Nursery

Dear followers (including Dr. Losos' Harvard uni freshman class),

I have a legitimate excuse for not posting during the last field season. I finally broke down and purchased a new camera body. Unfortunately, because I shoot in RAW, and Nikon seems to change this format every few cameras, my old-2008-macbook's version of iPhoto could not seem to process my recent photos. After much chagrin, I found freeware online that allowed me to batch and convert a group of photos from RAW to jpeg all at once! Woohoo!

Anyways, I have been back from the field for nearly a month now and I am eager to show you some of my new sparkling photographs and do a little sum-up of the highlights of this year's field season.

When we came back to the field at the end of July, the desert was a nursery of scaly and feathered young. The barn swallows are always nesting around the White Sands visitor centre- very cute. Very inquisitive, and overwhelmed by instinct, likely to open their mouths in synchrony when you pass your hand in front of their nest.
Young barn swallows outside the WSNM visitor centre.

Momma (or poppa) black-throated sparrow making a racket
outside the nest.

Isaiah also happened to look down the right bush and see a black-throated sparrow nest just 1.5 feet from the ground!
Adorable hatchling black-throated sparrows. 
Enough of the feathered creatures, you say! Where are the tiny cute little lizards we're all waiting to see!? Fortunately, I have some for you. Last year, times were tough- little rain brought fewer delicious insects, larvae, and spiders and thus fewer offspring. As such, we noticed far fewer yearlings/juveniles this spring. This year, however, butterflies fluttered everywhere, it was greener (for a desert), and we saw babies of each of the three White Sands species!

Hatchling A. inornata. This little guy is 'dark' and when we nabbed him outside the visitor centre, the people there scolded us for handling the lizards- until we said we were Herpetologists! 

The cutest little H. maculata we decided to name "Drew." (mainly because I misheard when Jackie said, "It's true!")
Baby lizards getting into some mischief with Jackie and Mikki... and Drew clearly knows which spot to best show crypsis on my foot!

Tiny little S. undulatus in the heart of White Sands.
I'm going to sign off for now and continue the sum-up of this last field season with a new blog post. Stay tuned- for later this evening!

Until then!
-S. Des Roches

28 July 2012

Back at it!

Well, it certainly has been a while!

Last I blogged about our Outreach day- which of course, was a blast. We finished up the last few weeks of the beginning-of-the-activity-season-field-season-part-one shortly after our kid's outreach days. Overall, we had fairly a fairly successful recapture rate for Holbrookia maculata... which was, funny enough, almost exactly 50%. We finished the field season with 175 successful captures, 87 of which were previously tagged from last year- either in the beginning or end of the activity season in 2011. We captured 145 Sceloporus undulatus and tagged every single one.

Male Lesser Earless, H. maculata, on the ecotone
Female Lesser Earless, H. maculata, in the heart of White Sands
We also chanced upon some exciting other finds... which may be considered predators roaming around our interdune sites!

Male Collared Lizard, Crotaphytus
, we named"Tyrone Lizardser,"
 for obscure, irrelevant reasons 
Gopher Snake, Pituophis catenifer, basking
between two interdunes on the ecotone

We have now just started the second recapture of S. undulatus and have decided that three weeks is not enough time to sufficiently sample H. maculata as well. So far, our recapture rate is not as good... after two days, we've collected 32 lizards, only 8 of which... or 25%... are recaptures.

Beautiful little Eastern Fence, S. undulatus, looking a little miffed at
being poked, prodded, and "processed"
Does this say something about the biology or ecology of this species? Is our study going to be effective at measuring natural selection by mark recapture over two years for S. undulatus? Whether or not we will be able to gauge the strength and direction of selection on this species, is yet to be determined... however, at the very least we can obtain informative population data, discover something about the robustness of mark-recapture methods for measuring natural selection across species, and spend just a few more weeks in the sun chasing after reptiles!

My favourite shot of an Eastern Fence Lizard just hanging out.

Until next time,
S. Des Roches

24 June 2012

Outreach: White Sands

Good afternoon!
Well, it is about time I spoke a bit about our adventures putting on our outreach program last week. On Thursday and Friday we led a "Lizards of the White Sands" day camp for local kids ages seven to fourteen as part of the White Sands Institute (which is an organisation that runs various classes for the public to enjoy the national monument).
This year is our second year running the event so fortunately we had a working schedule:

I. Introduction to White Sands, lizard ecology, and evolution.
II. Pack up with lots of water, sunscreen, and sunglasses to go out to the dunes.

Isaiah, Mikki, and I before the Natural Selection Game.
III. Natural selection game:
I divided the group of kids into 1/3 Roadrunners, or "Predators," and 2/3 Lizards, or "Prey." (on the first day, we had 21 kids - 7 predators, 14 prey; on the second day, we had 12 kids - 4 predators, 8 prey... much more manageable)...
Before the game.
Explaining the rules.
We picked an enclosed interdune where the Lizard-kids were given two dark-painted lizard toys, and one white-painted lizard toy to hide in various locations - under bushes, in the open, and on top of yuccas. I told the kids to make sure they remembered where they set their models. While the Lizard-kids were placing their basking models, the Roadrunners had to turn around and close their eyes (no cheating!). 
Ready to let the kids loose for the game.
After the kids had placed all their models, the Roadrunners had less than a minute to gobble up as many lizards they could find (I had to cheat a bit myself and check how many models they had in their hands before calling them back)... i.e. selection

Now... the tricky part... after the Roadrunner-kids' return, I sent the Lizard-kids to go check and see which lizards survived the feast. I then gave Lizard-kids one lizard toy of the same colour for every one they had left to indicate reproduction and inheritance. After their return, it was again the time for the Roadrunner-kids to feast as another round of selection. We played for only two generations... but I imagine with a greater proportion of prey-to-predators the game could go on for many more (our lizard population depleted pretty rapidly as a result of high predation). 

Go Roadrunner-Kids!
To drive home the entire point of the game, I then asked all players- Lizards and Roadrunner-kids to go collect all lizard models that remained in the interdune and pile them up in front of me. I asked all the children how many dark and how many white lizards were out to begin with. On the first day, with 21 kids, we had 14 x 2 = 28 dark lizards and 7 x 1 = 7 white lizards... i.e. the ratio of 2:1 dark:white.
Setting out lizard models.

Laying out the day's catch.

At the end of the game, we had the same number of dark and white lizards - 9 of each. I explained that this is how we think white lizards came to be on White Sands, via natural selection
Explaining natural selection.

This process takes many generations (where the lizards have babies like themselves), which is why you don't see white lizards taking over rapidly after only one reproduction event - they increase in proportion gradually; over time there are more and more lizards that match the white gypsum substrate of White Sands, or camouflage, and fewer and fewer that stand out.

IV. Catching the three species and learning about their ecology
What were the lizards doing when you first spotted them? What is the shape and colour of each species? How do you tell a male from a female?

Kayla showing her troop a little striped whiptail.

V. Return from the dunes and observe the lizards closer, and if time permits, try noosing some of those lizard toys!

The three funniest comments from the two days? (embarrassingly two came from my mouth):

3. (during my introduction talk) Me: "White Sands is very very young compared to the age of the Earth... it is only about 6,000 years old."; Kid: "So it's like a baby?"; Me: "Yes, White Sands is a geological baby"
2. (after drawing a horned lizard on a sheet of paper) Kid: "How big are those lizards?"; Me: "Oh about the size of your fist"; Kid: "So... like the size of a hairball... like a cat's hairball?"; Me: "Uh, sure..."

1. (when describing ecology in White Sands) Me: "Lots of predators eat lizards... roadrunners, snakes, shrikes, large lizards."; Kid: "Would a coyote eat a lizard?"; Me: "Well, maybe if they were desperate... but lizards are really small compared to coyotes and it may not be worth it for the coyote to chase around such a small meal... it's like if you were to run around after a Cheeto."

Participants showing off their lizard mugs.
We also gave the kids fantastic mugs that our advisor Erica Rosenblum had made featuring my design!

As usual we had a fantastic time with the kids- definitely one of my highlights of the summer. We are certainly fortunate to work in White Sands where we have the opportunity to put on such outreach programs! Thank you to my assistants, Isaiah, Mikki, and Jackie for helping me out this year, to David Bustos and Joan Griggs for doing the logistical work and advertising to get the camp running, and finally to my advisor Bree for letting us take charge and providing the foundation for the program!

Good day for now! Only one catching day left! Stay tuned for a season-recap and some photographic highlights!

-S. Des Roches