A study sheds light on the elusive animal behind the mascot
Like many and much more nimble Neotropical fauna, sloths are running out of room to maneuver.
As forests in South America and Central America are cleared for agriculture and other human uses, populations of these arboreal leaf eaters, which depend on large trees for both food and refuge, can become isolated and at risk. But one type of sustainable agriculture, shade-grown cacao plantations, could become critical refuges and bridges between intact forests for the iconic animals.
In Costa Rica, CALS forestry and wildlife ecology professors Jonathan Pauli and Zach Peery are using a complex of intact tropical forest, pasture, and banana and pineapple plantations—all connected by a large, shade-grown cacao farm—as a field laboratory to explore the ecology of two species of sloths in a rapidly changing environment.
“We know a lot about sloth physiology,” says Pauli. “But when it comes to sloth ecology and behavior, we know almost nothing. It’s a giant black box.”
But some of that mystery is being peeled away as studies of both the brown-throated three-toed sloth and Hoffmann’s two-toed sloth, two common species, are yielding new insights into their mating habits and how the animals navigate the landscape.
The fact that sloths require forested habitat and are sedentary makes them vulnerable to deforestation, says Peery. “Once a tract of tropical forest has been cleared, sloths have relatively little capacity to seek out new habitats.”
But the shade-grown cacao plantation, with its tall trees and network of cables for moving the pods that ultimately become chocolate, seems to be a de facto refuge and transit hub.
“Because of the diverse overstory of native trees, the cacao farm appears to provide excellent habitat for both species of sloths,” explains Peery. “We want to compare sloth populations in cacao to populations in intact tropical forests to see if cacao provides habitat that is of as high a quality as their natural forests.”
Fleshing out those ecological parameters, however, requires a better basic understanding of sloth behavior, knowledge the CALS researchers are now beginning to accumulate.
For example, in a study recently published in Animal Behavior, Pauli and Peery described the mating system of Hoffmann’s two-toed sloths and showed that, unlike many other animals, the females tend to disperse from their home range and that the breeding territories of males can slightly overlap, with males tolerating competitors on the fringes but excluding them, sometimes violently, from the core. And Hoffmann’s two-toed sloths of both sexes seem to have multiple partners as well. “They’re more promiscuous than previously thought,” says Pauli. “We see a much more flexible system of multiple matings.”
That’s not so for the three-toed sloth. In another study, published in PLoS ONE in December, they found that three-toed sloths are strongly polygynous—males exclude other male competitors and mate with many females.
In addition to contributing to basic sloth knowledge, these findings should help wildlife and land managers in the Neotropics make sound decisions to better balance development and conservation.
“Understanding how shade-grown agriculture can benefit sensitive tropical animals such as sloths is highly relevant, considering the ongoing and rapid loss of biodiversity in the Neotropics,” notes Pauli. “What kinds of ecological services can these already altered landscapes provide? Can we mitigate future biodiversity loss with a greater emphasis on shade-grown agricultural systems than crops grown in monocultures? That’s the future we’re facing.”
Because of their sedentary nature and dependence on forest, sloths can be viewed as an “umbrella species,” says Peery. “Protecting sloths could indirectly protect many other animal species in tropical forests that are harder to measure and study.”
Not long ago, one of the most biologically and culturally diverse regions on earth—Yunnan Province on China’s southwestern border, with its great river gorges, sweeping grasslands and majestic Himalayan mountains—was virtually inaccessible to outsiders.
Golden snub-nosed monkeys, black-necked cranes, snow leopards, Tibetan bears and an astounding number of other animals and plants thrive in its temperate forests and alpine meadows. And five million people from 26 of China’s 55 ethnic minorities live in the province’s remote high-altitude forests and valleys.
This biologically sensitive region has for the past half-dozen years been a field site for collaboration between the University of Wisconsin–Madison and the Chinese Academy of Sciences in Yunnan, a partnership that focuses on biodiversity conservation and sustainable development.
The idea arose from conversations between visiting scientist Ji Weizhi, former director of the Kunming Institute of Zoology at the Chinese Academy of Sciences (CAS) in Yunnan, and Kenneth Shapiro, an emeritus professor of agricultural and applied economics who was then associate dean of international agricultural programs at CALS.
“Ji was impressed by the interdisciplinary approaches that some of the UW departments were using to address complex problems like biodiversity conservation,” says Shapiro. “Ji could see that the traditional narrow ‘stovepipe’ or isolated discipline approach to biodiversity research cannot bridge the gaps in understanding diverse problems in biodiversity conservation. He understood that scientists needed a broader understanding of the relationships between the biology, livelihoods, economics and politics of Yunnan to protect its biodiversity and promote sustainable development.”
Yunnan’s name roughly translates to “south of the colorful clouds”—and indeed, the province’s beauty is self-evident. Less obvious, perhaps, is its environmental importance. The region provides critical ecological services across much of Asia. To take water alone as an example, nearly half of China’s population, along with millions of other southeast Asians, depend on the fresh water passing through the Three Parallel Rivers of Yunnan Protected Areas, which lie within the drainage basins of the Yangtze, Mekong and Salween rivers. If the natural forests in this region were destroyed, vast areas and populations downstream would suffer from severe floods and huge reductions of water supplies and quality.
After centuries of semi-isolation, Yunnan—the northwestern part of the province in particular—has been discovered by China’s new middle class of tourists, most of them Han Chinese, who make up more than 92 percent of China’s population. Where only hikers, horses and mules trod before, roads are being built by local and provincial governments to carry millions of tourists. Old-growth forests are being logged to accommodate them. Yunnan’s ethnic communities are having to transform centuries-old land use traditions. And the government is pressing Yunnan for economic development. Ji was aware that transforming Yunnan could have devastating effects on its biodiversity, on China’s fresh water supplies and on the livelihoods of ethnic minorities.
What Yunnan’s scientists needed was a model of an interdisciplinary approach to sustainable development and biodiversity conservation. Collaboration with UW, it was hoped, would mark a pioneering step toward developing that model.
Shapiro and other UW scientists, led by the late Josh Posner (see sidebar on page 27), found a home and funding for their part of the partnership under the auspices of IGERT (Integrative Graduate Education and Research Traineeship), a highly competitive National Science Foundation program that supports scientists and engineers pursuing graduate degrees in fields that cross disciplines and are deemed to have broad societal impact. The UW proposal drew on the strong support of the staff of CALS international programs, and the research also benefited from significant supplementary funding from the Graduate School, the chancellor’s office and the CAS.
Nineteen UW doctoral students, called “trainees,” were selected from disciplines ranging from political science and economics to conservation biology and anthropology, and included five CALS trainees from agronomy, forest and wildlife ecology, and community and environmental sociology. All participants were expected to learn Mandarin Chinese and, beyond their own disciplines, become literate in other fields relevant to conservation and sustainable development. While in Madison, trainees also attended weekly seminars on Northwest Yunnan’s history, politics, culture, society and ecology.
While some trainees received help getting their initial permits and contacts in Yunnan, it was up to each of them to work through such daily obstacles as getting around, finding translators for the many dialects and gaining the trust of locals.
Most trainees had done some kind of international work before joining IGERT. For example, Jodi Brandt in forest and wildlife ecology had worked in Guatemala with the Peace Corps, and community and environmental sociologist John Zinda had lived and taught in China.
When she first came to UW from Manitowoc, Ashya Kaderabek-Vela already knew she loved genetics, in part for the answers genetics seem to hold in explaining various health-related conditions that were passed down in her family. Initially her career goal was to become a genetic counselor. “I would be able to help other families understand [...]
For Wisconsin farmers dealing with wild swings in weather, adaptation is the key.
Qatar’s reserves of oil and natural gas make it one of the richest countries in the world—except when it comes to water. The desert nation is notably low on water, and what little it has often is salty.
It may sound unlikely. Certainly it sounds idyllic. But there’s a university course where professors may interrupt class to watch sturgeon swim by, and where lectures may be delivered from the bottom of soil pits or gathered around a campfire.
It’s Forestry Summer Camp, a three-week course offered by the forest and wildlife ecology department at CALS’ Kemp Natural Resources Station near Minocqua. The camp, which takes place every other year, introduces students to the information and skills they need to assess a forest’s natural resources—and also gives them ample opportunities to practice those skills in the field.
“It helps us get an idea of forestry and what it entails to see if it’s a good fit for what we want to do in the future,” says CALS junior Kelsey Egelhoff, who attended camp along with 26 other students this summer.
The department’s idea is to have new forestry majors take the course as early as possible. “It’s meant to provide new students with the excitement, the motivation and the context they need to do well in their remaining courses,” says forest and wildlife ecology professor Eric Kruger, one of the camp’s three coordinators.
Early on, students are divided into groups of four and assigned 250-acre tracts of land, called “compartments,” in the nearby Northern Highland American Legion State Forest to survey over the coming weeks. But even just the first step—setting up a compartment’s research plots—is no small matter.
Egelhoff estimates that her group walked for eight hours one day, guided by GPS, to mark their plots with red-flagged stakes—and they only got halfway done. “But even if it’s hard work, just being outside and getting to enjoy it all is really nice,” says Egelhoff, who hopes to go to graduate school and study redwoods in California.
Next the groups use modern tools and techniques to assess the birds, reptiles, amphibians, mammals, soils, woody debris, shrubs and trees on their plots, gathering data for a summary of their compartments and a final research project.
“One unique feature of our camp is that we have students explore the data that they collect and answer specific questions that are pertinent to their interests,” says Kruger.
The camp experience, he adds, has value beyond motivating students.
“I would guess that most employers have been through similar camps in their lives and fully appreciate the importance of these camps for the development of young professionals,” Kruger says.
Doug Soldat thinks there are better things to do with Wisconsin’s drinking water than use it to grow grass.
Nationwide, landscape irrigation sucks up about seven billion gallons of potable water on an average day—and probably two-thirds of that get sprinkled on home lawns, the CALS/UW-Extension soil scientist and turfgrass specialist estimates. Adding to the problem: We tend to all do it at the same time, particularly during hot, dry spells.
“The issue is reducing peak demand in municipal areas,” Soldat says. “As we put in more lawns and irrigation systems, we’re seeing higher peak demand, which means we have to build more wells and water towers.”
Soldat is looking at several strategies to address the issue. He’s got downspouts at the O.J. Noer Facility for Turfgrass Research flowing into the mother of all rain barrels, a 4,000-gallon underground reservoir that can see the center’s large lawn through a lengthy dry spell. He’s also developing guidelines for irrigating lawns with treated waste-water. That’s common in arid regions, and he suspects it will work even better in Wisconsin, where there’s ample rainfall to flush the soil of any salts the wastewater carries.
But one of the simplest solutions is to plant grass varieties that need less irrigation than, for example, Kentucky bluegrass, the most commonly planted grass in Wisconsin. One of the most promising, he says, is tall fescue.
“It has about the same water needs as Kentucky bluegrass, but its deeper roots give it access to more water in the soil,” Soldat explains. “It has double or triple the root mass of Kentucky bluegrass, so you could potentially double or triple the amount of time before you need to irrigate.”
Just how the two will match up during a dry spell is something Soldat is testing this summer. He’s growing several cultivars of each, along with a couple of other species, under severe drought conditions. That’s not easy in Wisconsin, where droughts are short and unpredictable. So he’s inducing drought with a rainout shelter—a 2,500-square-foot vinyl canopy on tracks. It sits off to the side when the sun is shining, but at the first hint of rain, it rolls into place to keep plots dry.
The drought tolerance work is part of a larger effort by the UW turf management team to provide information on reduced-impact lawn care strategies that work in Wisconsin. They offer suggestions in a new publication, “Organic and Reduced-Risk Lawn Care,” available at UW-Extension county offices or online at learningstore.uwex.edu.
Wisconsin residents of all ages and backgrounds are tracking wolves, monitoring streams, banding birds, counting invasive plants and more—all in the name of “citizen science”
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Numerous lakes and streams are drying up in the Central Sands, but there’s little agreement on what’s causing it. An initiative led by CALS brings together scientists, farmers, residents, environmental advocates and other stakeholders to shed light on the problem and pave the way toward solutions.