December 12, 2013
Most of Chicago's major zoos and museums are more than just showpieces for their collections, animal or anthropological.
Two new scientific studies — both based in the Bahamas and deriving from 18 or more years of work there — highlight the roles such institutions play outside their own boundaries.
Shedd Aquarium researchers, with help from citizen scientists, have studied iguanas on uninhabited Bahamian islands and determined that the snacks tourists are giving them — ranging from junk food to grapes — are not doing the animals any favors.
Meanwhile, a Field Museum scientist just published work proving for the first time what has long been suspected: that female sharks return to their birthplace to have their own litters. His methodology, at the museum lab he heads at the Field, included parenting tests very similar to the ones TV's Maury Povich uses for less lofty purposes.
The link between distant research and the Chicago headquarters may not seem apparent to the museumgoer wandering the galleries, but to staff it is crucial.
"In the zoo and aquarium world in general, we're moving away from just being these arks for animals that are extremely threatened," said Charles Knapp, the Shedd's vice president for conservation and research and its lead iguana man.
"There is a direct conduit from field programs to the 2 million guests we get a year," he said. "We have a privilege to have the animals here at the aquarium, and we consider them ambassadors for their counterparts in the wild."
But there are also personal passions at play. Ask Knapp how iguanas persuaded him to change his research and conservation focus from fish, and you'll get an earful: "For me (iguanas) are survivors. These animals are durable. They're tough. They're the largest native land animals on the islands they inhabit throughout the Caribbean. They have a personality to them."
Kevin Feldheim, manager of the Field's Pritzker Laboratory for Molecular Systematics and Evolution and lead author of the paper on lemon shark birth behavior, said his shark interest "stems from the fact that I wasn't able to see 'Jaws'" when it came out, along with some years in childhood living near the ocean.
Because the Shedd has been working 20 years in the Bahamas, collecting specimens and pushing for conservation, Knapp noticed when northern Bahamian rock iguanas in uninhabited portions of the nation's Exuma islands started being visited more and more by tourists.
Instead of shying away from the intruders, the animals, classified as a critically endangered species by experts, were flocking to the visiting boats. What the iguanas had learned, of course, is to expect food from the tourists.
"It happened so fast," said Knapp. One year, he'd rarely see iguanas in an area. The next, after a tour operator started taking visitors there, "all of a sudden (the iguanas) are going out on the beach and I see 15."
Knapp's paper, published last week in the online journal Conservation Physiology, compares the health of iguanas on Exuma islands regularly visited by tourists with those on islands that aren't.
Working with "citizen scientists" who pay to go on the Shedd's research vessel each spring, Knapp's team collected blood and fecal samples from iguanas in the Exumas in 2010 and 2012.
The comparison of visited and non-visited populations revealed they had equal stress levels, but the tourist-fed iguanas had loose feces, a 100 percent rate of endoparasitic infection and higher glucose and lower potassium levels, probably from grapes having become the tour operators' iguana food of choice.
"The purpose of the paper was to outline that, yes, there are indeed physiological and nutritional effects from tourism and feeding — so now what do we do?" Knapp said.
"We don't necessarily want to say, 'No more visiting and no more feeding.' Having these iguanas as a tourism (draw) will hopefully elevate their importance to the Bahamaian government," he said.
So his recommendations, which he said he'll be able to make directly to officials because of the aquarium's long history in the Bahamas, include replacing grapes with more nutritious food pellets, varying the diet from just grapes (and keeping the wet fruit off the sand so the animals don't ingest sand), limiting the number of beaches in the Exumas being visited and "also perhaps a dollar from each ticket can go toward conserving where these people are visiting," said Knapp.
The shark study was possible because scientists, led by Samuel Gruber of the Bimini Biological Field Station and the University of Miami, have been studying lemon sharks in the Bahamas' Bimini islands since 1995. By 2008, the first offspring from that cohort would have reached sexual maturity.
And fellow scientists — his paper required "a huge collaboration of many, many people," Feldheim said — found a mother first tagged in 1995 and then, nearby, her offspring.
Two animals weren't enough to get the paper published, he said, but the discovery in 2012 of four offspring, identified by DNA, of another of the early Bimini female sharks proved more conclusively that expectant sharks were returning to their birthplaces and led to the paper published last week in the journal Molecular Biology.
"The most exciting part of the whole project for me was when they caught the first female in 2008 and knew she was born there, knew she was pregnant, and then actually caught one of the babies later that year," Feldheim said.
The discovery that female sharks return to their birthplace to give birth — natal philopatry — not only furthers understanding of shark behavior, he said, but suggests conservation efficiencies could be achieved by protecting areas where sharks return to breed during breeding season.
Feldheim said his lab's work has continued despite deep budget cuts this year at the Field: "The lab has been really fortunate. In one sense, yes, we've lost some really good people. We currently don't have a fish curator. At the same time the museum is still making the kind of research we do a priority."
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