Saturday July 10, 1999
A sexually confused national symbol
Recent research seems to show that most male beavers have a uterus. Donna Jacobs tries to find out why.Donna Jacobs
The Ottawa Citizen
The symbolism is inescapable. Just south of the nation's capital, in the South Nation River, Canada's national animal -- the beaver -- lives in profusion. And sexual confusion.
Spencerville trapper Darcy Alkerton provided 11 male beavers to a research team at the University of Guelph's Ontario Veterinary College. Two professors there were looking for something specific and they found it in 100 per cent of the males -- a uterus.
They also found the "male uterus" in 70 per cent of the 13 beavers from Timmins, Algonquin Provincial Park and Guelph.
They already knew about the anomaly -- a fluke finding during their 1980s research at the university to develop more humane traps. Routine post-mortem examinations on beavers in that study turned up a very high percentage of males with a uterus.
"It surprised us," says Ken Fisher, a professor of biomedical sciences at the Ontario Veterinary College who specializes in embryology. "It's unusual. It's strange. That's why it came to our attention."
The finding may someday officially tag the North American beaver, Castor canadiensis, as a pseudo-hermaphrodite -- an animal that has sex organs from both genders.
Virtually all male mammals, and possibly all sexually reproducing creatures -- from humans to chickens and frogs -- are thought to have some small remnants of female sexual parts. However, a recognizable uterus is not a routine finding in a male mammal. In wildlife, it might normally occur once in 1,000 males, says Gary Partlow, a neuroanatomist in the biomedical sciences department who worked on the study. Or, he says, once in 100,000 males.
The Guelph researchers now have more questions than answers. Do these uterus discoveries reveal an unknown, but normal, anomaly in beavers? Or do they implicate a genetic defect or an environmental gender-bender pollutant?
Mr. Fisher says he hasn't discounted environmental pollutants, but at the moment supports the theory that a male uterus is part of a beaver's normal genetics and embryology. "I wouldn't bet the farm on that," says Mr. Fisher. "I'd bet a cup of coffee. If there were no literature about male uteri in beaver, and these were the first findings and observations, then I'd have red flags waving like crazy."
Mr. Partlow says he doesn't attribute the anomaly to chemical compounds because it seems to be unique to beavers and because the test beavers came from a large geographic area that probably do not have any one chemical in common.
Controversy still surrounds these sex-tampering chemicals, he says, including the possible link to a steep decline in the number of healthy human sperm in North American and European men. He cites the suspected estrogenic effect of many common substances, such as bisphenol A, a plastic ingredient in food-can liners, in some water-cooler water jugs, and even in sealants applied to children's teeth.
"I don't think these substances are a contributing factor in the male uterus of the beaver, but it is an issue that needs to be addressed. It's something that's creeping up on us," says Mr. Partlow, "and we may wake up one day and find that we have a disaster on our hands with the environmental estrogens."
These apparently bizarre findings of male-with-womb beavers are not absolutely new. But no one has been looking very hard at beaver anatomy, either. In the scientific literature, only three references to North American beavers describe male sex organs. Two of these, in the 1800s, contradicted each other. But because the second of them, in 1899, found no female parts, scientists assumed that Canadian male beavers are strictly male. Then, in a 1958 study in the U.S. northwest, a researchers found that 100 per cent of male beavers studied there carried a uterus.
Bryan Rennie of North Augusta, midway between Smiths Falls and Brockville, helped collect and dissect the beavers as part of his degree in biomedical sciences at the University of Guelph. He says the male uteri vary greatly in size, but basically look like that of an immature female's. He wanted to know whether the structure might interfere with male sex organs and discovered that it did not. The females showed no anomalies.
Even at this speculative stage of research, the male-womb finding is far from universal. John Knight, professor at the fish and wildlife department of Sir Sandford Fleming College in Peterborough, has also received beavers from trapper Darcy Alkerton. None of the males, he says, had a uterus.
To further confuse the issue, in all European beavers, Castor fiber, males carry a uterus and are well-known as pseudo-hermaphrodites. (A true hermaphrodite, such as an earthworm, is so-well equipped with both gender's reproductive organs that no matter which gender it meets on the mating grounds, it's always the right one.)
Embryology may provide some clues. It is generally believed that in mammals the female is basically the default species. That is, if no androgens (male sex hormones such as testosterone) are produced, the animal will be female. "One of my vet students wrote on an exam that a male is nothing more than a female," Mr. Fisher chuckled, "who has been poisoned by androgens."
In the female embryo, the tissue that develops into a uterus is both located next to the primitive kidney and is hormonally influenced by it. In the male beaver, the tissue would normally disappear. The agent of destruction is a protein-hormone that acts with testosterone to cause the cells of the embryonic uterus to "commit suicide," says Mr. Fisher. The male then absorbs the female structure.
The Guelph study, published last year in the Canadian Journal of Zoology, coincides with the Canadian government's decision to research "gender-bender" substances -- plastics, pesticides, sewage and industrial pollutants -- under investigation for causing sexual and other physical deformities in wildlife and possibly in humans.
The beaver study provoked no response from provincial or federal governments. Mr. Fisher says that he is not surprised by the silence, because the study raised questions that can be answered only with future research. He attributes the lack of interest shown by agriculture, health or environment departments to a shortage of scientists. "I don't think the personnel exists in federal or provincial ministries to be able to follow that research literature. I think they're stretched as thin as they can get."
He laments Canada's desertion of basic, curiosity-driven research. "There is overwhelming evidence that all basic research pays off," he says. "Jonas Salk was able to develop the Salk vaccine because for 40 years, people had been working on tissue culture. That investment was absolutely necessary."
And, in the mystery of the male beavers, the leap to applied research is not large. The male uterus is a well-known, if relatively rare, syndrome in humans. Men are usually unaware of it, unless they have a tumour in their testicles that triggers production of estrogen. This, in turn, causes the uterus lining to thicken or causes cysts or urinary problems. In humans, as in most wildlife and in domestic animals, the syndrome often causes infertility.
Mr. Fisher is critical of both federal and provincial governments and politicians for not funding continuous monitoring of wildlife populations. "What's going on with the beaver? We'd have to have field biologists out there counting beaver and looking at the health of the individual animal to be able to understand whether the population is stable, or going up or whether in a particular area, it's declining."
A 40-per-cent cut in environmental funding, he says, has shut down such monitoring.
"We do an abysmal job of testing water and the environment. It's much more sexy to have the Canadarm floating around in space. If you were really cynical, to quote my students, there is a vested interest in not collecting data," he says, "because you don't have to respond and fix anything."
The news of sexually strange male beavers breeding in the local swamps and ponds that feed the South Nation and Rideau rivers has captured the attention of nearby residents.
Katherine and David Jeffrey are neighbours of Mr. Alkerton at RR2, Spencerville. She is a book editor and he is professor emeritus of English at the University of Ottawa. The Jeffreys heard -- with some distress -- about the "remarkably large number of gender-confused beavers" because Mr. Alkerton traps beaver in their creek. Mrs. Jeffrey's fears that some of the beaver that went to the University of Guelph came from her creek may be well-founded.
Mr. Alkerton says he might have trapped the beaver in the Limmrick Forest, and is certain that all came from within five miles of his house. The Limmrick Forest, a provincial park, backs onto the Jeffreys' organic farm.
Mrs. Jeffrey says that reports that pesticide ingredients may disrupt human and wildlife endocrine systems is "extremely alarming," since her farm is flanked by dairy farms and corn fields and lies downstream from other farms.
"We have never had this creek tested," she says. "If someone wanted to do it, I would be delighted to know what's in it. I think it is full of chemicals since there is agricultural runoff from farms upstream."
Naomi Langlois, fish and wildlife technician from the South Nation River Conservation Authority, says that the water nearby had been tested two years ago, when the authority hired Mr. Alkerton to remove beaver from a section of the river before it began a dredging project. "We would have flagged something rather unusual, but I don't think anything major was flagged."
Further, she said, the area is the beginning of a 4,000-square-kilometre river drainage system and at this high elevation, "you typically don't have a lot of contamination there." Farming is the only industry.
Because beaver are so plentiful in Ontario -- they're considered pests for flooding agricultural land and roads -- their ability to reproduce has not been questioned. Mr. Alkerton does not live-trap them, as he does some other species, because there is no demand for their relocation.
But the mystery of the male womb remains. Mr. Alkerton says he has contacted 20 people at the provincial and federal agriculture and health departments and the ministry of natural resources about the Guelph findings.
"Nobody will reply," he says. "There doesn't seem to be anybody interested." The University of Guelph's veterinary school, which usually concentrates on domesticated animals, has done the seminal work on these wild beavers. But to settle the issue, says Mr. Fisher, requires three further studies to determine:
- whether the male uterus is a normal part of male beaver anatomy by studying a larger sample from more diverse regions;
- whether the male uterus causes infertility by breeding healthy animals;
- and how the uterus develops and what is interfering with males' normal ability to simply absorb it away.
Bryan Rennie, who dissected the male wombs, graduated and now works with cattle at Eastern Breeders in Kemptville. He sometimes holds up the Canadian nickel and tells people: "You see this animal? It's a pseudo-hermaphrodite." But the truth -- whether the beaver represents a natural sexual oddity or an environmental casualty -- points to yet another Canadian identity crisis.
Copyright 1999 Ottawa Citizen