Mammalogist Katherine Ralls remembers the first time she picked up the book "Living Mammals of the World," by Ivan Terence Sanderson. Flipping through the pages, she saw a big-cheeked pocket gopher burrowing in the grass, a caracal with its elongated, tufted black ears. It was hunching over a small white mole, a Colombian night monkey with burnt umber eyes starring directly back at her. What does it see, she wondered? As her fingers traced the lines of a zebra, a teenage Ralls pictured herself in Africa watching the herds graze on the Serengeti. She showed the book to her mother and pleaded with her to buy it. It cost $35, a lot of money in 1955.
Gripping the book tightly, Ralls left the store, triumphant. "That's when I knew," she says, \I'm going to study mammals."
For 46 years, Ralls has enjoyed a wide and varied career in mammalogy and conservation biology. She was among the first biologists to recognize the importance of applying scientific methods to conservation efforts. She helped found the Society of Conservation Biology in the mid-1980s and pushed for the field to have its own place in academia.
Ralls worked on the first radio-transmitter implants and tracking of California sea otters in the mid-1980s and on the population, diet, and range of California's endangered San Joaquin kit fox — a furry critter about the size of a house cat. Ralls has written almost 20 papers on kit foxes and shows no signs of slowing. Her current focus: genetics and parental care. "The fathers are very involved with the babies," explains Ralls.
Listen as Katherine Ralls discusses her fieldwork on California sea otters and kit foxes
Her early work at the Bronx Zoo on animal scent-marking has long been considered a "classic" amongst zoologists. Ralls fondly remembers telling the zoo curator, \"Find me an animal with lots of scent glands and interesting behavior," she says with a laugh. He took her straight over to the Maxwell's duikers — little African antelopes with "huge scent glands below the front corners of the eyes," says Ralls. She makes two fists with her hands and places them on her cheekbones, adding, "the male and female rub their scent glands on each other and all over their environment."
But Ralls is perhaps best known for diagnosing inbreeding depression of animals at the Smithsonian's National Zoo in Washington, D.C in the late 1970s, where she was hired as their ungulate [hoofed animals] expert.
Today, zoos closely manage captive populations to preserve genetic diversity. With the help of a studbook and database software, zookeepers can trace the pedigree and entire demographic history of all animals in a captive population, which they use to determine another zoo where an animal should be sent once it reaches reproductive maturity.
Learn more about current captive populations by watching this video featuring lions, zebras and Golden Lion Tamarins
Before Ralls' work, zoos paid little attention to genetics. The accepted scientific consensus of the time was that inbreeding in captive populations was not problematic. She spent nearly a decade convincing them they were wrong.
Sitting in the backyard of her newly remodeled home in Carmel, California, Ralls, 72, tucks her shoulder-length blonde hair behind her ears and smoothes her bangs to the side. Along the fence, a trio of house finches take a break to enjoy the morning sun.
She pauses for a moment and then begins: "I sort of stumbled onto it, the inbreeding problem...I don't really know why no one else hadn't noticed before me." It was 1978, and Ralls, an eager young scientist from California, had just started a comparative study on mother-young behavior of the zoo's ungulates. She had a large volunteer staff at her disposal, so she busied them with data collection. She told them to track the animals' daily activities: Are they standing up? Are they lying down? How many "mother lengths" away is the baby? Are the babies followers or hiders? And so forth. "It was fairly simple work," she says.
Not long into the project she noticed a lot of the young animals were dying soon after birth. Ralls narrows her eyes, saying, "I remember the reindeer, five out of the seven died."
Ralls went looking for answers in the zoo's well-kept records. She traced most of the deaths to father-daughter matings.
Thinking it was an "easy fix," she advised the zoo to separate related animals. "Oh no, there was great resistance to this idea," Ralls says straightening up in her chair. The zoo felt that moving the animals around could injure them, and there was backwash among the zoological community, where consensus was that inbreeding "really isn't a problem," she said.
Many of the zoo managers came from livestock husbandry backgrounds where healthy inbreeding takes place routinely. Additionally, mice had been inbred successfully for decades for research purposes.
Ralls realized that if she was going to change things she'd have to build a stronger case. She grabbed a summer intern and together they got to work. Ralls looked at 16 species of ungulates, starting with the Dorcas gazelle. "I had not even figured out an inbreeding coefficient at the time — I said, 'Just tell me if the parents are related or unrelated and whether they died before they got to six months old.'" In 15 out of 16 cases, including the Dorcas gazelle, the inbred mortality rate was significantly higher than in the non-inbred animals. They reported their findings in Science in 1979, concluding inbreeding could be a problem in small wild populations but was "definitely a problem in zoos."
It was a dud. Many within the zoological community felt it was a "hoofed animal" problem only. "Not the primates," one scientist told her.
By this time, Ralls had hired a young, bright biologist named Jonathan Ballou to work with her. Together they went back into the National Zoo's records and began assembling data on primates and small animals — 45 species by the time they finished. Their findings were the same as the ungulates — inbreeding caused increased mortality.
Meanwhile scientists came back at her with a barrage of "alternate hypotheses." Maybe it's an overcrowding issue, or inbred mothers not having maternal instincts, they argued. Together Ralls and Ballou went about disproving each theory. "We had to plug all the escape holes for the zoo community," Ralls says.
Ralls and Ballou then had to show that accepted inbreeding in mice and livestock was not a good model for zoos to follow.
Creating healthy inbreed lines of mice is actually a difficult process often resulting in extinction. The lab mouse was created under very careful controls — 20 consecutive generations of sister-brother matings, but about 19 of the 20 attempts fail. Ralls and Ballou argued that zoo managers just didn't understand what went into the development of healthy inbred animals, but used it as the basis for how they managed their captive populations. Many were not familiar with the literature on the deleterious effects of inbreeding in laboratory and domestic animals because it was published in the 1930s and '40s.
The director of the Bronx Zoo, who knew Ralls from her work with the duikers, helped sway the community. He felt she was onto something and had his staff look at their own data and plot mortality over time. Their findings were the same as Ralls and Ballou. Convinced, he used his influence with other zoo directors to change their minds.
In 1986, Ralls and Ballou hosted a national workshop on genetic management for zoo animals. They invited genetic experts to come together and develop breeding guidelines for zoos to ensure the long-term biodiversity of captive animals. Their recommendations: Establish populations that are large enough so that the population will only become 10 percent inbred over the next 100 years; use pedigrees to make sure that all the genes are preserved, making sure males and females are unrelated to the best extent possible; and routine monitoring of the health of the population to detect any genetic problems should they occur.
Zoos across the country acted quickly to adopt the guidelines and agreed to team up so they could pool their animals into one much larger managed population. Today there are over 2 million animals of approximately 10COMMANUMBER000 species held in nearly 650 zoos in over 70 countries being genetically tracked, according to the Naples Zoo website.
Back at her seaside home in Carmel, Ralls spends her days advising government agencies on endangered mammals, mentoring a younger generation, and researching kit foxes and sea otters. Ralls is pleased she could make a difference in the lives of captive animals, helping to preserve them for the next generation. "I really just like to find things out about animals, especially mammals\" she says adding, \"there is always more to learn."
- Smithsonian National Zoo: Katherine Ralls biography | Sea otter research | Kit fox research