Marlene Zuk (Philadelphia, Pennsylvania, United States, 1959) completed a BA in Biology at the University of California, Santa Barbara in 1977, and a PhD in Zoology at the University of Michigan in 1986. After a postdoctoral stay at the University of New Mexico, in 1989 she joined the University of California, Riverside, where she would become Professor of Biology, as well as Associate Vice Provost for Faculty Equity and Diversity. In 2012 she moved to the University of Minnesota, where she is currently Regents Professor of Ecology, Evolution and Behavior. Author of more than 180 published scientific papers and five books, and the recipient of 19 research grants, she has been president of the International Society for Behavioral Ecology and vice president of the American Society of Naturalists, as well as a visiting professor at Uppsala University (Sweden) and visiting scientist at the University of Western Australia. Among her editorial positions, she has served as editor of Behavioral Ecology.
The BBVA Foundation Frontiers of Knowledge Award in Ecology and Conservation Biology has gone in this fifteenth edition to Susan Alberts, Jeanne Altmann and Marlene Zuk “for their outstanding contributions to the behavioral and evolutionary ecology of animals,” in the words of the award citation.
“Behavior”, explains the award citation, “is a primary means by which individuals respond and adapt to ever-changing conditions, including shifts in their social environments. These three scientists have extended our understanding of the evolutionary and functional significance of behavior in driving animal survival, reproduction and fitness.”
For the committee, “the work of Alberts, Altmann and Zuk enriches our understanding of the need to incorporate social interactions into conservation plans for animal species.”
Altmann, Professor of Ecology and Evolutionary Biology, Emerita at Princeton University, and Alberts, Professor of Biology and Evolutionary Anthropology at Duke University, have devoted their research careers to studying diverse aspects of baboons’ social behavior, while Zuk, Professor of Ecology, Evolution and Behavior at the University of Minnesota, has explored how male-female interactions or those between parasites and their hosts explain mating preferences, elucidating the role of sexual selection in species diversification.
“With the research done by the three awardee scientists we can achieve a perfect X-ray of the health and physiological state of individuals within a species that is potentially at risk of extinction,” explains Pedro Jordano, CSIC Research Professor at the Doñana Biological Station and secretary of the award committee. This information, he adds, is a vital input “to optimize the selection of individuals for inclusion in reintroductions or captive breeding programs, and thereby ensure their success.”
The social life of baboons
In 1963, Jeanne Altmann traveled to Amboseli National Park in Kenya to conduct a thirteen-month study on the baboons living in this nature reserve. A few years later, in 1971, she returned to set up an innovative research project, which over five decades has followed some 2,000 individuals across several generations, and continues to this day.
The Amboseli Baboon Project quickly gained an international name, leading Susan Alberts to choose it as her first research destination in 1983, right after graduating. And so began a four-decade collaboration between the two scientists, who have pioneered the study of baboon social behavior.
Alberts currently co-directs the Project along with Altmann and another two scientists – Elizabeth Archie and Jenny Tung – who were their nominators for the Frontiers Award. “Thirty-nine years ago we were both told we shouldn’t be doing this,” Altmann recalls, “and we kept being told that for about 15 to 20 years. But the extent to which the project was paying off for us personally and professionally, and also for the field, was becoming increasingly clear.”
Their observations taught them, for instance, that male baboons take an active role in caring for their offspring. Despite multiple-mating by both males and females of the species, baboon fathers, it turns out, can distinguish their own infants from those of other males and look out for them accordingly, demonstrating what Altmann and Alberts refer to as “true paternal care.”
Altmann suspected that this was the case, but was only able to prove it through the genetic analysis of fecal samples, a study she and Alberts conducted together. With the DNA extracted they were able to identify the paternity of each infant and verify whether the caring behavior came from the biological father.
“For several decades now, for instance, we’ve been collecting fecal samples from known individuals, and we now have freezers full of thousands of these samples from which we can extract DNA, microbiota and hormone metabolites, and all of these compounds give us insight into what’s happening to animals physiologically, stress levels for instance, as they face the challenges they encounter every day,” Alberts explains.
Getting similarly under the skin of female behavior in animal societies has been a constant focus of Altmann and Alberts’ research. But to do so, says Altmann, they have had to break a few molds: “There was a fair bit of literature saying it was just the big males and the relations of dominance among them that mattered, but we were able to show quite early on that the females in the group and the relationships they formed were vitally important.”
Alberts believes that her mentor “was actually a very central player in what became a shift in the entire field towards a greater understanding of primate social behavior.” Females, they found, play just as large a role in driving social processes as males, and can switch from being allies to competitors, and vice versa, in a very short time, denoting a highly complex social environment.
One advantage of studying baboons is that the research can extend over whole generations. In effect, she and Altmann, Alberts observes, have had the chance to follow several generations of primates over their full lifespans in a long-running field study that is a landmark of its kind.
The role of parasites in sexual selection
Marlene Zuk’s research has shed new light on the importance of parasites in determining animals’ social behavior. “We used to think that these organisms were just the causes of diseases, a terrible thing. But they actually play a role in shaping not just whether or not we get sick, but in everything that their host organisms do: how they choose their mates, the way they interact with each other… Because avoiding parasites and disease has been a primary driver of evolution,” said the scientist, who was advised of the award while traveling to Australia for a one-year research stay.
It is precisely Zuk’s study of insects that has laid bare “the universality of the forces of evolution in animals so different from humans.” For this scientist, behavior is just one more characteristic of the evolution of living beings.
“Animals don’t just interact with each other or with members of the opposite sex,” she points out. “They’re also affected by parasites and pathogens that change the traits that females might find most attractive in a mate.”
Zuk speaks from her direct, personal observation of the rapid evolutionary response of a cricket species to the pressure exerted by a parasite. In general, male crickets use a mating song to attract females, so natural selection tends to favor those that sing loudest and best. But the song of a particular type of cricket attracts not only females, it also grabs the attention of a parasitoid fly that deposits its larvae in the cricket, larvae that then burrow into its body and eat it from within.
The male, then, experiences a conflict that springs from the struggle between sexual selection (obtaining a mate) and natural selection (survival): the more it sings, the more it will attract females, which is what it needs to pass on its genes. But, at the same time, its chirps attract the fly that may eventually destroy it, a clear evolutionary disadvantage. As Zuk remarks, “it is these conflicting selection pressures that act in exactly opposite directions that have fascinated scientists since Darwin.”
What the ecologist observed was that, in a few generations, a mutation spread through the cricket populations that rendered them silent. This meant they were less prone to being detected by the fly, but with the adverse effect of reducing their attractiveness to the opposite sex. Evolution, in other words, bends this way or that depending on the pressures of the environment.
“This constant push-pull of evolution has always enthralled me,” says Zuk. “And what it underscores is that evolution doesn’t stop.”
Another transformative finding was her demonstration of the determining role played by parasite-host conflict in evolution by sexual selection. Evolutionary forces should favor females choosing males that are resistant to disease, leading Zuk to inquire whether males had evolved ways to signal this resistance.
She realized that the ornaments characterizing the males of many animal species, like the tails of peacocks, are a way to signal their resistance to parasites. So when a female chooses a male with particularly elaborate ornamentation, she is choosing a mate resistant to infection by these pathogens. These mechanisms play a decisive role in the evolution of many animal groups.
The importance of the social environment in animal health
Another, broader conclusion of the awardees’ work is the importance of social interaction for animal health and survival, and thereby the evolution of the species. For example, Alberts and Altmann have deduced from their study of baboons that, for these primates, strong social bonds are linked to longevity, and, in the case of females, also positively predict offspring survival.
“The work that we’ve been doing has helped us understand that the social environment is just as important as the physical environment in determining health and survival, for our study species and many other organisms that are highly social creatures,” Alberts relates. “What this means,” she continues, “is that animals are using social behavior to solve the problems in their environment, and the diversity of ways in which they do this has taught us about the many different solutions to the problems of the environment that have evolved over the millennia.”
Key tools to support species conservation
Altmann, Alberts and Zuk’s scientific contributions on how the sociality of animals shapes their health and survival have become key tools for endangered species conservation strategies. “Mating systems and sexual interactions are a big issue in conservation, because ultimately they determine the viability of a given population,” explains Francisco García González, a researcher at the Doñana Biological Station who has worked with Zuk and co-signed papers with her. ”When females choose a mate, what they are doing in essence is to choose genetic quality. Sexual selection is tied in with reproductive success, and therefore population viability. So when implementing a conservation plan, it is vital to bear in mind the kind of socio-sexual interactions and mating behaviors elucidated by the prizewinning scientists.”
Although many conservation actions target iconic species, Zuk is at pains to stress that “animals that are not big and furry can turn out to play incredibly critical roles in the evolution of biodiversity.” The parasites she has studied for decades are a case in point: “Animals don’t exist in a vacuum either in terms of their interactions with each other or their interactions with other species,” she insists, as her cricket research shows so well.
Hence the importance of studying inter-species networks in depth so we can learn how best to protect them: “We can’t conserve something if we don’t know whether it’s there to begin with,” she affirms. “I think a lot of people think that what we want to conserve are the big, so-called charismatic megafauna, the elephants and the pandas, but I am just as concerned about preserving the little things, the small animals that really can matter: the pollinators, the scavengers, the animals that are hidden away in the grass, and if we don’t understand what they’re doing, and we don’t understand their biology, we’re never going to be able to save them.”
Altmann and Alberts have witnessed in these past decades how the baboons are noting the twin impact of global warming and habitat degradation. “At the moment what’s happening is a terrible drought in Amboseli, one of the worst in the past 50-60 years. And this is happening because of changes in how humans use the landscape and also global climate change, which increases the probability of droughts in that type of habitat.”
From their latest studies, the two conclude that baboons can serve as models to study the adaptability of many other animals to environmental degradation. As Alberts says: “By carefully documenting and studying how baboons can accommodate and adapt to, or fail to adapt to, various degrees of habitat change, we can gain insight into how many different types of species are likely to respond in the face of such challenges.”