Archive for October 2010
Sometime tonight or in the next few days, take the time to listen to this conversation on the beauty of science between Richard Dawkins, the famous evolutionary biologist and author, and Neil deGrasse Tyson, the astrophysicist and director of the planetarium at the American Museum of Natural History. You won’t regret it. (I listened while doing the most thorough clean of my apartment since I moved in. So productive!)
It’s a very interesting conversation – - the beauty of science, much speculation on the origins of life and intelligent life elsewhere (as you might expect from a clash of evolutionary biology and astrophysics), and, generally, simultaneous wonder at how much we know and how little we know.
But more than anything, here is a conversation between two of the greatest minds and communicators n science out there now. They’re a little competitive, sure, but even though they are from different disciplines, their excitement just oozes from them. The bromance is evident and it’s worth listening for that alone.
So take the hour. Play it in the background when you’re doing housework later, or paint your nails, or knit, or whatever you crazies do. It’s AWESOME!!!!
It has been ingrained in all of us that these are fearsome facts, that the very low population of a species means they are close to extinction (and with good reason). But when you think about what this means – that a smaller population is less able to recover and grow in size – it doesn’t make perfect sense at first. A small population should have more resources available for each individual because there is less competition within the species. Additionally, there should be overall less predation on a lower population because, in a simplified model, this population will support fewer predators, and the predators are less likely to preferentially seek out a scarce animal in favor of other prey. (For a primer on population ecology, check out this one I wrote up here.) Why shouldn’t the animals be able to reproduce and increase the size of their population?
Despite these caveats, we see the pattern repeat itself: when a population of a species gets small enough, it seems to get stuck there, unable to recover its numbers. Instead, it continues to shrink.
What is the cause of this? In the 1930s to 1950s, an ecologist named Warder Cylde Allee described what was known afterwards as the Allee effect, this pattern of a decrease in the per capita reproductive rate in a species when the population gets to be too small. Of course, “too small” is a variable number depending on the species and its life history traits, such as feeding preferences, natural range, and social behavior.
This is a notably difficult theory to study because it requires a foresight that we lack. Identifying a species that is already at a critically low population isn’t enough. To provide evidence for the Allee effect, scientists need to identify a threatened population before it becomes threatened in order to collect data on its range, foraging behavior, and social activity, and compare these data to similar traits when the population has gotten “too small.” But if we had this sort of foresight, we hopefully would put in enough effort to prevent the population from dropping in the first place.
I am sorry to report that such a species has been identified, one that is on the brink of extinction: the Vancouver Island Marmot. This large rodent (5-7 kg! 70 cm long!) is geographically restricted to Vancouver Island, and evolved rapidly after its arrival after glacial retreat 10,000 years ago. It is an herbivore and lives in large burrowing colonies. The cause of their population drop (from 300 animals in the 1980s to 25 (25!) in 2001) is not entirely clear, but is thought to be associated with increased logging. A possible cause is that the clearcut forest from logging looked like prime meadow for setting up colonies, but the quick regrowth of these forests uprooted the colonies, scattering the animals.
A clear Allee effect in this population is shown in the figure below, from a study by Justin Brashares (UC Berkeley), Jeffery Werner (UBC) and A. Sinclair (UBC) in the September 2010 issue of the Journal of Animal Ecology. At the right side of the curve, decreases in Vancouver Island marmot population size resulted in a higher per capita reproductive rate. But at a certain threshold (around 200 marmots), the curve turns downward, with a decreasing reproductive rate with decreasing population size. This Allee effect is so evident from these data that I may as well have copied this figure from a population ecology textbook.
The authors wanted to explore what changes in the marmots’ behavior caused this decrease in reproductive rate. What exactly prevents these animals from reproducing effectively and recovering their population? They collected data on the marmots’ activity budgets (where they spent their time) for comparison with a similar set of data from the 1970s. They also used similar marmot species for comparison, as they only diversified 10,000 years ago.
They first looked at the modern home ranges of the marmots compared to other closely related species. As they are colonial animals, marmots don’t frequently leave their burrow, and do so on a daily basis only to forage. Males will leave to seek mates at other burrows, but historically burrows have been very dense and thus the males would not have to travel far. As shown in the figure below, the Vancouver Island marmots have a modern range ten times larger than any other social marmot species. This increase in travel and distance from their colony increases their exposure to predators, as they no longer have the alarm calls and protection of their colony. The authors hypothesize that the marmots have increased their range due to a lack of mates nearby. Thus the very process of increasing their reproductive rate is hindered because they cannot find mates, and when they go looking, are more likely to be killed by predators or get lost in unfamiliar territory.
The authors also observed drastic changes in their social behavior. Compared to historical Vancouver Island marmot behavior and that of other related species, the modern population spends far more time on watch for predators (nearly two-thirds of their above-ground time!), as predator populations have increased since the 1970s. But despite these efforts, far fewer alarm calls were heard per animal, indicating that there are still not enough animals to properly stand watch for the colony. By spending so much time on watch, they lose time for feeding, risking starvation, and forcing them to go into hibernation later, risking freezing to death. Time in the burrow also increased, perhaps in an attempt to hide from predators and rest from the constant vigilance and lack of energy from decreasing foraging.
It’s a sad picture these authors have shown us. These social rodents are travelling far distances alone in search of a mate, and spend most of their active time watching for predators instead of foraging for themselves and their offspring. So hungry! So cold! And despite all this effort, their reproductive rate continues to drop! Is there any hope?
The hope we have is in reintroduction programs. The idea is that if we are able to successfully breed large numbers of marmots in captivity and raise them so that they can be reintroduced properly, we can increase the population to a suitable level that these animals are able to find mates and start reproducing again. The Vancouver Island Marmot Foundation has a recovery plan and has been working to reintroduce the animals, which it has been able to do successfully. (You can see their recovery plan on their website.)
I have long been a critic of zoos because I didn’t see how their conservation benefits outweighed the impacts of captivity on the animals kept there. But this is why they are important. The key is to keep a certain wildness in the animals so that, if their population does drop low enough to show an Allee effect, we have some hope for adding more animals to the population to help save the endangered species.
Brashares, J., Werner, J., & Sinclair, A. (2010). Social ‘meltdown’ in the demise of an island endemic: Allee effects and the Vancouver Island marmot Journal of Animal Ecology, 79 (5), 965-973 DOI: 10.1111/j.1365-2656.2010.01711.x
Donors Choose Initiative: if helping school children wasn’t incentive enough, I’ll draw you a picture!
My earliest memory of engaging with nature and science took place in my grandparents’ backyard in Roslyn, NY. It must have been the summer, and I walked up to a tree and found a weird brown thing stuck to it: a cicada exoskeleton. I still remember the feel of the little shell, the papery abdomen and the way the little hairs clung to my skin. What is it? How did it get there? Where is the insect now? How many are there? … ad infinitum in the way of a curious child.
Many of us interested in nature and science have an early memory like this. It’s the child’s “sense of wonder” that Rachel Carson describes in her book by that title. I have returned to this quote over and over again throughout the years and, although it’s long, I encourage you to read it right now:
A child’s world is fresh and new and beautiful, full of wonder and excitement. It is our misfortune that for most of us that clear-eyed vision, that true instinct for what is beautiful and awe-inspiring, is dimmed and even lost before we reach adulthood. If I had influence with the good fairy who is supposed to preside over the christening of all children I should ask that her gift to each child in the world be a sense of wonder so indestructible that it would last throughout life, as an unfailing antidote against the boredom and disenchantments of later years, the sterile preoccupation with things that are artificial, the alienation from the sources of our strength.
While adults certainly can appreciate nature, it does feel that childhood is the time to craft the experiences that will lead to an appreciation of nature and science throughout life.
If facts are the seeds that later produce knowledge and wisdom, then the emotions and the impressions of the senses are the fertile soil in which the seeds must grow. The years of early childhood are the time to prepare the soil. Once the emotions have been aroused – a sense of the beautiful, the excitement of the new and the unknown, a feeling of sympathy, pity, admiration or love – then we wish for knowledge about the object of our emotional response. Once found, it has lasting meaning. It is more important to pave the way for the child to want to know than to put him on a diet of facts he is not ready to assimilate.
I was lucky: I grew up in a family that was familiar with the natural world, and in an area full of outdoor space to explore and experience. Not everyone is so lucky. But if Rachel Carson is right, as I believe she is, about the importance of having nature/science experiences as a child, we need to do our best to provide support teachers as they try to provide fodder for wonder while their students still have time to ask, “why?”
Here at the Southern Fried Science Network, we’re trying to help teachers instill a sense of wonder for ocean science through the Science Bloggers for Students challenge through the Donors Choose Initiative. If you even have $5 or $10 lying around, donate it to a classroom of your choice to pay for supplies so teachers can do their jobs and teach awesome lessons about ocean science! Check out the Gam’s page here. (We are in competition, technically, so it would be great if you donated through our page. But really we’re competing FOR THE SAKE OF THE CHILDREN so any donations are acceptable.)
If helping kids wasn’t enough, I will provide another incentive: Hannah Waters original drawings of a sea creature of your choice! Forward your receipt or some proof of donation to hannah.waters [at] gmail [dot] com and I will mail you a “beautiful” original drawing. Hell, even if you don’t donate through the Gam I’ll do it for ya. That’s how much I care about the children.
So Donate, Email me proof, I will mail you picture that you could have asked your 10-year old to draw for you.
Edit: If you donated before I posted this, I will grandfather you in and draw for you in thanks!
I am no artist: I just like drawing animals when I’m watching TV. Here’s some examples of my work that I did on Saturday while watching BSG:
Hope to hear from you!
(cross posted from Sleeping with the Fishes)
Yesterday, Jeremy Yoder directed me (via twitter/his blog) to a new blog: the Molecular Ecologist. I was drawn to it because, well, I’m interested in molecular ecology. But when I got to the site, I got a little over-excited. This is a blog run by the academic journal Molecular Biology Resources, but they want to do more with the blog than just self-report. Their description:
However, we’d like to do more to support the molecular ecology community as a whole. This blog is a step in that direction- a forum for readers and contributors to the journal to discuss the latest papers and trends in the field. Future additions to the site include a comprehensive, searchable list of computer programs and other code (e.g. R packages) useful for analysing genetic data; and a site where novel lab methods can be posted and discussed.
PEOPLE: THIS IS WHAT THE INTERNET IS FOR.
Every academic journal should have a blog! It doesn’t have to be fancy; Molecular Ecology Resources just started up a simple WordPress account. But this creates a space for discussion, sharing of information, to publish additional information such as interviews, and more. I think it’s a great way to get the researchers to do a bit of blogging and share their stories and their research.
It would be self-promotional, that’s for sure. I’m sure the blog will publish many write-ups of their own articles. But if they hold true to their word and try to discuss other important research and trends in the field, it could be very beneficial to the molecular ecology community and be a great model for other disciplines.
Maybe this sort of thing exists elsewhere, but I haven’t seen it done so simply. So good job, Molecular Ecologist. I hope you take this somewhere wonderful and set a great example for other journals.