Archive for December, 2013

That the earth’s climate is changing has become a well established fact, but determining exactly how these changes will effect ecosystems is still an area of active research.  Within this scope of research, how climate change will effect animal behavior is a particularly understudied topic.  But, a recent presentation at the 2013 Animal Behavior Society conference gave an interesting example of just that.  The information presented was on where the Pantless Tree Frog (Dendropsophus ebraccatus) decides to lay its eggs.  This species, which is found throughout Central America, sometimes lays its eggs on the underside of leaves and at other times lays them in the water.  Each location has advantages and disadvantages.  Laying eggs in water mean that they are pretty much guaranteed to sty moist, but there are predators in the water that eat frogs eggs, so more clutches fail due to predation.  Laying eggs on leaves exposes the eggs to much lower rates of predation, but if the eggs dry out they die.  Generally, conditions in the range of the Pantless Tree Frog are quite rainy and so the frogs choose the option of avoiding predation and they lay their eggs on leaves.

However, as the climate has changed rain storms have become more and more sporadic over the last 4 decades, and are likely to become even more so in the future.  This has meant that Pantless Tree Frogs are having to lay their eggs in water to prevent them from drying out.  However, this leaves them open to the greater predation rates.  When predation rates go up on a species, the population level of that species usually finds a new equilibrium level that is lower than before the predation rates rose.  And smaller populations are classically more vulnerable to be reduced further by natural disasters like floods or droughts, and experience higher likelihoods of extinction.

In this way, the Pantless Tree Frog is an excellent example of how changes in an animals’ behavior, in this case in response to climate change, can have important conservation implications.

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Beginning now, and continuing until early January, something amazing is happening.  Thousands of  people are going out into the world around us and participating in the annual Christmas Bird Count (CBC)!  Christmas Bird Counts are systematic counts that cover particular geographic areas and are repeated each year.  They have been conducted every year since 1900 making the CBC the longest running citizen science project ever.

Before 1900, famous ornithologist Frank Chapman wanted to create an alternative option to the Christmas hunting competitions that were common at the time.  It used to be that people would go out into the field and see how many birds they could kill.  Chapman wanted to harness this energy and enthusiasm for the outdoors and direct it towards something that could benefit the birds in the long term.  He decided that if people went out and counted the birds in an area each year, a valuable data set could be created and we could learn a lot about the birds around us.   To this end he organized the first CBC in 1900.  In that first CBC, a total of 27 people participated, and they counted birds in 25 different locations.  The CBC has grown tremendously since then.  In the 113th CBC which was last year, 71,531 people participated and counted birds in 2,360 different locations, and it is continuing to grow with more participants and locations expected this year.

And Chapman was right, we are learning valuable things about the birds around us.  Over 200 peer-reviewed papers have been published using CBC data!  One of the most significant findings that CBC data has revealed is the response that many bird species are having to climate change.  Of the 305 species that winter in the North America, 60% of them have shifted their ranges north by an average of 35 miles over the course of the last century.  This is generally interpreted as the birds needing to move farther north to find the appropriate foods and temperatures as global temperatures have risen.  Another prominent finding has been the tracking of the Bald Eagle and Peregrine Falcon recoveries since the banning of the insecticide DDT.  Populations of both species were drastically reduced in the 1950s and 1960s, but with the help of ornithologists and falconers have made dramatic comebacks!

Joining a CBC is easy.  Just contact local Audubon chapters and they will have a list of CBCs in your area.  More counters are always welcome.  So go out and participate in the 114th Christmas Bird Count, and help to continue this incredible legacy!

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The phylum Mollusca is one of the most diverse groups of animals in the world.  It includes familiar organisms, like the snail in our gardens, and not-so-familiar organisms, like the recently discovered Colossal Squid that cam grow to up to 33 ft long and weight 1,100 lbs!  This group is comprised of three major classes the Gastropods (slugs and snails), the Cephalopods (squid, octopus, cuttlefish, nautilus), and the Bivalves (clams, mussels, oysters, scallops).  Several more smaller groups exist as well.  In total, all these groups combined account for about 200,000 living species!  Ecologically, molluscs interact in many complex and important ways from decomposers to predators to prey.

Of the 200,000 species of molluscs, most are marine, but as we all know from everyday lives there are plenty of terrestrial molluscs as well.  At least for now.  Terrestrial molluscs have been experiencing dramatically high rates of extinction in the past half century.  The International Union for the Conservation of Nature (IUCN) publishes a Red List which identifies the conservation status of all species every five to ten years.  The IUCN has identified about 800 in the last 500 years, and of those about 300 are molluscs.  That means that about 40% of all extinctions belong to this one group, and some people have estimated the number of molluscs we have lost to be as much as double the IUCN estimate.

Most of these extinctions have taken place on small oceanic islands which is not surprising.  Ecosystems on oceanic islands are notoriously delicate, and extinctions often occur in response to ecological disturbances such as the introduction of some new predator, the clearing of land for agriculture, or competition with other newly introduced species.  Their fragility makes oceanic islands the canaries in the coal mines giving us early warnings of what might befall continents if we do not stop, or at least slow, the current rates of ecosystem disturbance.  On the Gambier Islands, for example, there were 46 species of terrestrial snail.  Of those 46 species, 43 are now extinct.  Many of them have not even been given names.

An interesting footnote is that while terrestrial molluscs are disappearing disturbingly quickly, marine molluscs are not.  Is there something about the marine environment that makes species that live there less prone to extinction?  Is it just that there have been fewer introduced pests and predators to oceans and to land (since land is where humans spend most of their time)?

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I just received the latest Time Magazine and was interested to read the cover article by David Von Drehle entitled “America’s Pest Problem: Why the rules of hunting are about to change.”  The article discusses how the populations of several species of North American wildlife have expanded in recent history to the point where they are now doing ecological damage and entering human dominated landscapes leading to damage and difficulties there.  Overall, the message of the article was that humans have caused these population increases, and so now need to play a more involved role in wildlife management to correct them, and that hunting should be a prominent part of that role.

I agree with this overall message, and it is one of the  major reasons I started hunting a few years ago.   The other possibilities for controlling wildlife populations generally fall into one of two categories: contraceptives or aversion training.  The idea behind treating animals with contraceptives is to reduce the birth rates of these species and so slowly reduce the population level.  However, this involves the sometimes quite difficult task of injecting the animals with the hormones by either capturing them and injecting them directly, or shooting them with drug loaded darts.  Either method of delivery is time consuming, usually results in a relatively small number of animals being treated, and is expensive.  Furthermore, the drugs usually do not work well, if at all.  Aversion training is when animals are disturbed by flashing lights, sirens, fireworks, lasers, rubber bullets, or other non-lethal devices frequently enough that the animals decide that they need to leave a particular area and go elsewhere.  This does not work for several reasons.  One is that in many cases the animals quickly learn that the lasers and loud noises don’t actually do anything, and so the animals simply ignore them.  Another reason is that human environments are so attractive to some species that they are worth suffering through some pretty serious annoyances to get to.  A third reason why aversion training does not work is that it assumes that there is empty habitat for these animals to move into.  In many cases, this is a very bad assumption, and the animals have no choice but to come back to the human dominated landscapes.  So, removing animals, permanently, from the population is one of few effective methods: a.k.a. hunting.

But, while I agree with the article overall, I was troubled by some points, and also the way in which some of those points were made.  First off, the subtitle “Why the rules of hunting are about to change” implies…well, that the rules of hunting are about to change.  Now, it is true that some cities scattered across the nation have changed ordinances that relate to hunting, but that does not mean that we are on the precipice of some major change in hunting laws at the state level or above.  Another, major, issue I take with the article is how the author mixes what should be viewed as good wildlife interactions in with troublesome wildlife interactions.  For example, in one paragraph, the author sympathizes for the plight of retail employees in Florida having to deal with alligators at their doorsteps (which could be quite dangerous) and office workers in New York who have a hawk nesting on the side of a skyscraper (which is a wonderful thing that has no detrimental effects on humans).  These are not the same category of wildlife encounter, and it seems misguided to lump them together.  Another worrying aspect of the article is that it plays into the commonly held fears about top predators.  Part of the article discusses how the increasing populations of prey species is allowing the populations of predators such as Grey Wolves, Grizzly Bears and Mountain Lions to increase as well.  The author states that hunting to reduce the prey populations will help to reduce the amount of human-predator interactions and so avoid “an invasion of fangs and claws.”  This kind of fear mongering is simply not appropriate.  The numbers of humans injured or killed by wild predators is ridiculously low.  Here are some rough estimates of deaths from large predators in all of North America since 1900: Black Bears = about 70, Grizzly Bears = about 70, Mountain Lions = about 20 people (which is fewer than the number of people killed by lightening strikes), Gray Wolves =  just 3.  A final issue that I take with the article is that is lumps native species and invasive species, and basically treats them the same.  One of the figures depicts the increases in population size of 10 species since the mid-1900s.  The caption for the figure says that these are 10 species that have come back from the brink of extinction; however, two species are Wild Pigs and Wild Turkey.  Wild Pigs are a non-native and highly invasive species that really should not be on this continent at all and have never been close to extinction, and Wild Turkeys are increasing in number partly because they were introduced to the western U.S. and are flourishing in this new habitat.  The management goals for these species are very different from, say, Beaver or White-tailed Deer or any of the other native species in the figure.

So, while I liked the message that hunting is a responsible and useful tool in wildlife management, I felt that the article was subtly misleading and definitely oversimplified, and such a portrayal is not in the best interest of hunting or wildlife management.

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