Can't Compete On Dung? Try Mating On Apple Pomace

SOURCE

ScienceDaily (June 27, 2009) — In the mating world of yellow dung flies, large, brawny males almost always get the girl. However, a new study suggests that smaller males rule if presented with an opportunity to woo females when they are not hanging out on cow dung. It is the first time alternative male reproductive strategies have been observed in this species.

In a study published in the June 24 Proceedings of The Royal Society B, a group of Syracuse University (N.Y.) undergraduate students found that small male dung flies, which are traditionally unsuccessful at finding and keeping mates on dung pats, successfully mated with females feeding on composting apple pomace. In fact, large males were generally absent from the pomace mounds.
"This is a new chapter in the story of yellow dung flies," says Scott Pitnick, professor of biology in SU's College of Arts and Sciences. "No one has carefully studied this species off the dung. Small male dung flies can't compete with their larger counterparts on the dung, so in this case, they developed a different tactic to successfully pass their genes to the next generation."
Pitnick co-authored the study with the students. The students were enrolled in an advanced biology course designed to teach them to conduct original scientific research. Pitnick co-teaches the course with J. Albert C. Uy. As part of the course, the students were tasked with designing a study around the size and mating success of yellow dung flies.
"After we made our initial field observations for the class assignment, we could tell from our professors' reactions that our discovery was a piece of important information in the field," says Stephen Maheux '09, a biology major who graduated in May. "The course was designed to teach us how to be biologists; as such, we made a unique observation that ultimately resulted in a publication."
Until now, it was thought that yellow dung flies mated almost exclusively on manure. Females are drawn to the dung only when they are ready to mate. Little is known about the feeding habits of females when they are not at the dung pats, Pitnick says. On the other hand, males were thought to hang out almost exclusively around the manure, awaiting the arrival of the females. Competition on the dung among males is fierce and can result in injury or death to smaller males as well as females caught up in the struggle.
But, on Toad Hollow Farms in Nedrow, N.Y., the students noticed large numbers of females feeding on apple pomace in a field adjacent to the cow pasture where they were observing flies on dung pats. Much to the students' surprise, the females were frequently mating on the pomace, and with males that were significantly smaller in size than those found in the cow pasture. Furthermore, none of the sexually aggressive behaviors normally observed on the dung pats occurred on the pomace.
Owned by Bill Guptill, Toad Hollow Farms produces natural compost made from manure, leaf and yard waste, and fruit and vegetable waste from grocers in and around Central New York. Apple pomace is the pressed pulp that remains after juicing. The students' initial observations suggested that the availability of the pomace seemed to provide male dung flies with alternative mating opportunities.
Maheux and biology major Kali Henn, who will be a senior in the fall, continued working with Pitnick after the class concluded to collect and analyze additional data, re-confirm the initial class results, and help write the manuscript that was submitted for publication to The Royal Society.
"The class focuses on enabling students to experience the research process—from formulating questions and making the observations to designing the experiments, analyzing the data and writing the final manuscript," Pitnick says. "In this case, what started as a class exercise ended up as a significant finding in this field."
Adapted from materials provided by Syracuse University.

Mate Selection: Honesty In Advertising Pays Off

SOURCE

ScienceDaily (June 19, 2009) — Throughout the animal kingdom brilliant colors or elaborate behavioral displays serve as "advertisements" for attracting mates. But, what do the ads promise, and is there truth in advertizing? Researchers at Yale theorize that when males must provide care for the survival of their offspring, the males' signals will consistently be honest — and they may devote more of their energy to caring for their offspring than to being attractive.

The idea that males showcase their best qualities to attract females for mating isn't a new one, nor is the idea that they might be deceptive in what they are promoting. Instead, the new findings better predict the requirement for honesty in advertising as a function of the male's suitability for parenting, according to Natasha Kelly, a graduate student in ecology and evolutionary biology at Yale and lead author of the study.
The peacock's ornate fanned tail — or the primping and posturing of a guy in a bar — are "advertisements" or mating displays that take substantial energy to maintain. When a male's energy is heavily focused on keeping up his appearance, he may have little energy to devote to caring for offspring. But that may be okay, say the researchers — in species where he does not really need to tend to the kids.
Previous research suggested that, under certain circumstances, males could be dishonest about their parenting skills and still have high reproductive success. This new model, now appearing in the online version of the Proceedings of the Royal Society B, examines the reliability of males' mating signals when they must care for offspring — an aspect that was missing in earlier studies.
There are many species in which males could, but do not have to, provide parental care — because females will pick up the slack. The Yale researchers focused on those species, like stickleback fish, where females cannot pick up the slack and males who do not provide care risk the survival of their offspring.
"This new work shows that when males can not escape the cost of failing to provide care, their advertisements will tend to tend to reliably indicate how much care they will provide," said senior author Suzanne Alonzo, assistant professor of ecology and evolutionary biology at Yale.
"The qualifier in this case is where males are obligated to provide care," said Kelly. "In that case, the quiet guy in the corner might be giving the more reliable advertisement for fatherhood."
The National Science Foundation and Yale University funded this research.
Journal reference:
Kelly et al. Will male advertisement be a reliable indicator of paternal care, if offspring survival depends on male care? Proceedings of The Royal Society B Biological Sciences, 2009; DOI: 10.1098/rspb.2009.0599
Adapted from materials provided by Yale University, via EurekAlert!, a service of AAAS.

Hunters Are Depleting Lion And Cougar Populations, Study Finds

SOURCE

ScienceDaily (June 18, 2009) — Sport hunters are depleting lion and cougar populations as managers respond to demands to control predators that threaten livestock and humans, according to a study published in the June 17 issue of PLoS One. The study was led by Craig Packer, a University of Minnesota professor and authority on lion behavior, who worked with an international team of conservationists.

The study looked at numbers of lions and cougars killed by hunters over the past 15 to 25 years in Africa and the western United States. The analysis suggested that management agencies often adjusted quotas to control rather than conserve the big cats in areas where humans or livestock were threatened.
Sport hunting takes a significant toll on these large feline species because replacement males routinely kill their predecessors' cubs to improve their mating opportunities. (Killing cubs forces female lions into estrus or "heat.") The team of scientists confirmed this effect by comparing the impact of hunting on populations of lions, cougars and leopards with its impact on black bear populations because male black bears do not routinely kill infants of other males.
Lion and cougar populations have suffered the greatest decline in African countries and U.S. states where sport hunting has been most intense over the past 25 years, the researchers found. Leopards were not as affected as lions and cougars, most likely because they benefited from reduced numbers of lions. Black bears, by contrast, appear to be thriving despite the thousands of bears killed by hunters.
The study results point to the need for new approaches to protect humans and livestock and to manage sport hunting without endangering these vulnerable species. One possibility would be to restrict sport hunting to older males whose offspring have matured.
"We need to develop scientifically-based strategies that benefit hunters, livestock owners and conservationists," Packer says. "It's important to educate the public about the risks these large predators pose to rural communities and to help hunters and wildlife managers develop methods to sustain healthy populations."
"Packer's colleagues included co-authors Luke Hunter, Executive Director of Panthera and Kristin Nowell from the International Union for the Conservation of Nature Species Survival Commission (IUCN/SSC) Cat Specialist Group, as well as Dave Garshelis, Chair of the IUCN/SSC Bear Specialist Group."
Journal reference:
Packer C, Kosmala M, Cooley HS, Brink H, Pintea L, et al. Sport Hunting, Predator Control and Conservation of Large Carnivores. PLoS ONE, 4(6): e5941 DOI: 10.1371/journal.pone.0005941
Adapted from materials provided by University of Minnesota, via EurekAlert!, a service of AAAS.

Biologists Close In On Mystery Of Sea Turtles' 'Lost Years'

Source:

http://www.sciencedaily.com/releases/2007/09/070928203128.htm

Science Daily — Biologists have found a major clue in a 50-year-old mystery about what happens to green sea turtles after they crawl out of their sandy nests and vanish into the surf, only to reappear several years later relatively close to shore.

In a paper set to appear Wednesday in the online edition of the journal Biology Letters, three University of Florida sea turtle scientists say they found the clue by analyzing chemical elements ingrained in the turtles’ shells.
Their conclusion: The turtles spend their first three to five “lost years” in the open ocean, feeding on jellyfish and other creatures as carnivores. Only after this period do they move closer to shore and switch to a vegetarian diet of sea grass – the period in their lives when they have long been observed and studied.
“This has been a really intriguing and embarrassing problem for sea turtle biologists, because so many green turtle hatchlings enter the ocean, and we haven’t known where they go,” said Karen Bjorndal, a professor of zoology and director of UF’s Archie Carr Center for Sea Turtle Research. “Now, while I can’t go to a map and point at the spot, at least we know their habitats and diets, and that will guide us where to look.”
The discovery is important not only because it’s a first, but also because it may aid in conservation of the turtles -- which, like all sea turtles, are classified as endangered. “You can’t protect something,” said Bjorndal, “if you don’t know where it is.”
The paper’s lead author is Kimberly Reich, a UF doctoral student in zoology who did the work as part of her dissertation research. The other authors are Bjorndal and Alan Bolten, a faculty member in zoology and associate director of the sea turtle center.
Famed sea turtle biologist Archie Carr first discussed the mystery of the green sea turtles’ “lost years” in his 1952 book, “The Handbook of Turtles.” Half-dollar sized hatchlings trundle off subtropical and tropical beaches worldwide, then vanish, only to reappear, dinner-plate-sized, over continental shelves in depths of less than 650 feet. Only a tiny number of green turtles between the half-dollar and plate-sizes have ever been spotted.
To solve the problem, Reich, Bjorndal and Bolten turned not to scouring the ocean but rather to a technique that over the past two decades has become increasingly important in questions related to ecological origin: stable isotope analysis.
The higher an animal on the food chain, the more heavy isotopes it accumulates. As a result, the technique, which measures the ratios of heavy to light isotopes, can distinguish samples from herbivorous versus carnivorous creatures and where on the food chain they lie.
The researchers captured 44 turtles off a long-term study site near Great Inagua in the Bahamas. The sample included 28 that had been tagged in previous years, indicating they were residents of the site, and 16 untagged turtles assumed to have recently arrived.
They cut off tiny pieces near the center of the turtles’ shells in a harmless process that Bjorndal likened to trimming one’s fingernails. The biologists used a mass spectrometer, a machine that separates isotopes according to charge and mass, to analyze the oldest, or earliest-grown, portions of the shell sample versus the newest portions.
The analysis revealed that with the new arrivals to the site, the ratio of light to heavy nitrogen isotopes in the older versus new shell samples was “significantly different,” as the paper said. The ratios were very similar to ratios observed in oceanic-stage loggerhead turtles known to be carnivorous. For these reasons, among others, the researchers concluded the turtles spend their first three to five years in the open ocean.
Green turtles nest on subtropical and tropical beaches worldwide. That suggests the young turtles are widely distributed in the oceans during their oceanic stage, but Bjorndal said further study is required to confirm that.
Green turtles are the ocean’s largest hard-shelled turtle, with only soft-shelled leatherbacks eclipsing their size. They were heavily exploited for food by native peoples and then by explorers and colonists who prized the animals for remaining alive and fresh for months on ships. Although they were among the first animals listed under the Endangered Species Act in 1973, they and their eggs continue to be hunted in much of their range today.
Said Bjorndal, “Anything that helps us discover geographically where they are is going to stand us in good stead to be able to protect them.”
Note: This story has been adapted from material provided by University of Florida.

Fausto Intilla

www.oloscience.com