Friday, December 9, 2011

Friday Roundup-Arctic Owls in the United States

1. Snowy Owls Venture South. I would venture a guess that many people in the United States would say the closest they will ever get to a Snowy Owl, Nyctea scandiaca, is a Harry Potter Movie. They might be surprised.

It has long been known that Snowy Owls from northern Canada periodically venture far south (here's one filmed in Tennessee in 2009). Last month, a Snowy Owl was photographed outside of New York City (click here to view the details and fantastic photographs). Their appearances in the United States tend to take place during the winter months. Perhaps as a result, many ornithologists (scientists who study birds) believed that when populations of small mammals (like voles or lemmings, which owls love to eat) decreased to very low levels, Snowy Owls migrated south in large numbers to find more food.

This idea persisted for a long time. Before I started investigating the NYC owl for this blog, I probably would have repeated that story to you. But, there is actually little evidence to suggest that Snowy Owls head south because of changes in prey populations. It is probably more accurate to think of Snowy Owls simply as a migratory species, just like many of the other bird species that can be found along the east coast of the United States. Many songbirds, for example, breed in the northeastern United States but spend their winters in Central and South America. Snowy Owls probably do something similar, they are just starting from further north. When you come from northern Canada, I suppose a New York winter feels relatively mild, there's no need to head all the way down to South America.

Two weeks ago, a pair of Great Horned Owls, Bubo virginianus, took up residence in some dead trees along a pond in my yard. At night their mournful hooting gave voice to the night. I only ever saw one, the owl was a dark silhouette against the sky in the last few moments of sunlight. After four nights, they vanished and I have not heard them since.

A Ctenosaur Surveying His Territory
2. Here Be Dragons. The largest lizards I have ever seen were the giant ctenosaurs (aka spiny-tailed iguanas) of Palo Verde, Costa Rica. Although equipped with an impressive set of teeth, they are largely herbivorous and timid creatures.

Those words have not often been used to describe the world's largest lizard, the Komodo Dragon, Varanus komodensis. Early European explorers feared encountering dragons during their expeditions, but their fears were generally unfounded unless they happen to be sailing through Indonesia, where they might encounter a the famed dragons of Komodo. These lizards are famed for their hunting strategies, which allow them to take down mammals much larger than themselves. A wild creature that most only know from books or nature programs on television, Komodo Dragons are the epitome of The Wild.

In his blog, Laelaps, Brian Switek writes about how Komodo Dragons became known to most of the world and describes early attempts to keep these incredible creatures in captivity. In the course of telling the story of the Komodo Dragon, Brian offers some commentary on the role of zoos; one cannot help but wonder whether observing a majestic creature in an enclosure can be compared to the experience of knowing you're sharing the landscape with one (or many).



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Much of what I write is based on my experience in the field, however I also rely on the research of others. Citations of some relevant scientific articles are included below.

P. Kerlinger, M. R. Lein, & B. J. Sevick (1985). Distribution and population fluctuations of wintering snowy owls (Nyctea scandiaca) in North America Canadian Journal of Zoology, 63, 1829-1834

Friday, December 2, 2011

Friday Roundup-An Octopus Invasion and a Hellbender Conservation Breakthrough

1. An Octopus Takes a Stroll. Perhaps you've come across the video of the octopus laboriously pulling itself out of the water and making its way through the intertidal zone.




The Octopus was found in the James V. Fitzgerald Marine Reserve on the California coast. By the sound of the voices in the video, it was spotted by a family exploring the area. Katherine Harmon (in her blog, the Octopus Chronicles) got to the bottom of this seemingly odd-behavior by a marine creature.


"Why would an octopus struggle across land, when its boneless body seems so unfit for moving out of water? For the chance to find some tasty shellfish and snails, most likely. When the tide goes down, 'many octopus species emerge to hunt in the pools of water left behind by the receding tide,' Finn (Julian Finn, an octopus expert) notes...After an octopus has cleared one tidal pool of food, it will often then haul itself back onto land in search of the next pool, which, Wood (James Wood, another marine biologist) notes, it might be able to spot visually, or detect ahead with its outstretched arms."


I don't have much to add. Pretty cool to imagine these ocean creatures taking advantage of terrestrial habitats.


2. A Breakthrough in Hellbender Conservation? Perhaps you recall me describing my attempt to find Hellbenders (Cryptobranchus alleganiensis, North America's largest salamander) in north Alabama a few years ago. Alas, we were unsuccessful. It turns out that our inability to find the species was not because we lacked the proper skills. A recently published article has basically said that there are no Hellbenders left in the entire state. Obviously, this is little consolation. 


Hellbenders need clear, unpolluted and undisturbed streams to survive and reproduce. They spend their entire lives in these streams and take refuge under large rocks. When the landscape around the creeks are disturbed, the result is too much silt and sediment, which covers all the Hellbender hiding spots. Unfortunately, this situation isn't unique to Alabama, and Hellbenders, which can be found nowhere else in the world but eastern North America, are in trouble throughout their range. Strategies to save the species are controversial, and there are many obstacles to recovery.


Hellbenders use unique habitats and its hard to replicate those clear, flowing streams in artificial settings. Not surprisingly, that makes it hard to get Hellbenders to reproduce in captivity. As a result, it is all but impossible to even consider reintroducing Hellbenders to areas where they've gone extinct (a strategy used for another animal previously extinct in Alabama, the Indigo Snake); there are simply no baby hellbenders to release back into the wild! But, the St. Louis Zoo recently announced that they had made a breakthrough. By creating artificial streams, they were able to construct habitats that made Hellbenders (technically Ozark Hellbenders, a subspecies) comfortable enough to produce offspring. Very innovative! Kudos to the St. Louis Zoo. My hope is that their success is paired with increased efforts to protect the Hellbender's natural habitat. Together, the two strategies may result in some long-term progress in bringing the Hellbender back to the areas where it has disappeared.


3. The South Florida Rainbow Snake Reward Stands. The $500 reward for any evidence that the South Florida Rainbow Snake, Farancia erytrogramma seminola, still exists, which I wrote about last week, has received some more attention. Most interestingly, it is noted that the Center of Snake Conservation is planning to gather some aquatic snake experts to conduct a search for the animal. I wonder what it would take to get in on that...


Finally, of all the keyword combinations people Googled this week that led them to this site, here are my favorites:


"chinese crocodile swimming to america"
"does anyone eat stuffed snake for thanksgiving?"
"getting along with wildlife david steen" (close enough)
"snapping turtle bit me lost a finger"
"secrets of giant snakes don't want the public to know"


I hope everyone found what they were looking for...







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Much of what I write is based on my experience in the field, however I also rely on the research of others, citations of some relevant scientific articles are below.



SEAN P. GRAHAM, ERIC C. SOEHREN, GEORGE R. CLINE, CHRISTINA M. SCHMIDT, WILLIAM B. SUTTON, JAMES R. RAYBURN, SIERRA H. STILES, & JAMES A. STILES (2011). CONSERVATION STATUS OF HELLBENDERS (CRYPTOBRANCHUS ALLEGANIENSIS) IN ALABAMA, USA Herpetological Conservation and Biology, 6 (2), 242-249


Crane AL, & Mathis A (2010). Predator-recognition training: a conservation strategy to increase postrelease survival of hellbenders in head-starting programs. Zoo biology PMID: 20973085