Can high-quality habitat be too much of a good thing?

It might seem like having lots of resources for feeding and breeding would be an all-around benefit for wildlife, but researchers found that for some species, poorer habitat can be beneficial when it comes to movement and habitat connectivity. As a result, they found, urban environments can play a bigger role for some species than people might expect.

“There’s a lot of interest in conservation biology in making landscapes more connected,” said Elizabeth Crone, a professor at Tufts University and lead author of a study on the benefits of lower-quality habitat for the Baltimore checkerspot butterfly (Euphydryas phaeton) published in Ecology. “The way we think about doing that is building networks or corridors of habitat focused on the best places for species to live.” But Crone and her colleagues found the best habitat connectivity for the butterflies may actually be areas that have fewer resources.

“They move more slowly through high-quality habitat, partly because there’s more things for them to do, partly because it’s better for them to be spending more time there,” she said. “They move more quickly through lower-quality habitat.”

The team was especially interested in the ability of species to move quickly through corridors in the face of climate change. She and her colleagues completed a meta-analysis of around 70 species to determine movement in lower- and higher-quality habitat, then homed in on Baltimore checkerspot butterflies. They found that the best landscape for them, in terms of range expansion, would be composed of 15% high-quality habitat and 85% lower-quality hayfields and farm fields.

For species to expand their range, they need to reproduce and move quickly, Crone said. This is particularly important in the face of climate change when some species are shifting their ranges to places where they can more easily survive.

It’s not just butterflies. Crone said researchers can plug information from other species into the equation they used to determine what proportion of high- and low-quality habitat is optimal.

The findings have implications for conservation in urban environments, she said, by suggesting that even modest habitat improvements can help a species persist, and that urban and suburban landscapes can play important roles in connecting natural landscapes.

“Nearly everyone wants butterflies in their garden and are happy to see them in the city,” Crone said. While urban planners figure out how to convert green areas to benefit butterflies on a large scale, she said, “it’s also something you could do now by planting a butterfly garden in your yard.”

When it comes to managing wild horses on public lands in the West, it’s hard to find common ground. Proponents thrill at the sight of free-ranging horses, and they appeal to concerns about animal welfare to protect them. Critics point to the ecological damage that the invasive species can do the arid landscape and to the other wildlife that share it. All sides of the argument can get emotional.

“I think the piece that resounds with everybody is, no one wants to see horses die of starvation and dehydration,” said TWS member Erik Beever.

Are there ways to achieve that, and to manage wild horses on Western lands, that will get various interests on board? It’s a question that Beever, a research ecologist with the U.S. Geological Survey Northern Rocky Mountain Science Center in Bozeman, Montana, raises in a perspective published in Biological Conservation.

The challenges confronting wild horse management run deep, according to Beever and his co-authors, Lynn Huntsinger, of the University of California, Berkeley; and Steven Petersen, of Brigham Young University. Solutions, they say, may come from the realm of social science as much as biology.

“There’s a very broad diversity of user groups,” Beever said. “Everything from hunting groups, to folks that have to deal with threatened and endangered species, to state and federal agencies monitoring water quality, to livestock producers, to conservation advocates, to rural landowners, to those who love the enigma of the ‘Wild West’ and its horses. The power and charisma of horses are two characteristics that horses have that facilitate them being deeply appreciated by humans. They’ve also been used in human societies for millennia. There’s a strong connection there.”

But there’s also a strong connection to changes horses can bring to the environment. The authors note that according to past research, the list of alterations that horses can bring to arid landscapes is long, from soil degradation to vegetation loss to reducing native ungulates, small mammals and reptiles.

Removing the horses entirely isn’t much of an option. The 1971 Wild Free-Roaming Horses and Burros Act calls for them to remain on the landscape. But management options, constrained by lots of other laws and regulations, are limited. Grazing regimes that govern domesticated livestock use generally can’t be implemented. Neither can hunting options that are used to manage wild ungulate populations.

The two means of controlling population sizes are immunocontraceptives and removals of animals to off-range holding facilities, called gathers, and both have drawbacks, Beever said. Gathering up the horses is expensive, as is caring for tens of thousands of animals in holding facilities for the remainder of their lives. Contraceptives, usually fired from dart guns from the air, are difficult to apply and limited in their effectiveness.

“You only have two tools to provide solutions,” he said, “and neither of those are particularly easy to implement nationwide.”

Their paper lays out a series of “mismatches” that make managing wild horses so hard. Managers seek target population numbers that the ecosystem can support, but conditions on the ground can change in a matter of days or weeks. The political process can demand fast answers, but science takes time. And in the court of public opinion, science doesn’t necessarily win out.

Solutions to the wild horse dilemma, the authors argue, are caught between “contradictions, constraints and mismatches.” To work through them, they suggest that tools from social science may be as useful as those from biology. Decision-making techniques, including structured decision-making and other tools, may be the most useful ways to reach compromises on what can seem like an issue with little common ground.

“Society is going to have to increasingly be making hard choices,” Beever said. “They’ve always been hard, but the choices become more limited, more difficult and more vexing over time.”

For frogs, a stressful early life as a tadpole can lead to long-term fitness consequences in adulthood.

“Even though you have this huge change in body morphology through metamorphosis, that doesn’t mean you’re going to be a completely different animal,” said Evan Bredeweg, a PhD candidate at Oregon State University and the lead author of a study published recently in Frontiers in Ecology and Evolution. “There are still going to be legacy effects.”

Bredeweg and his co-authors wanted to see how stress early in life might affect the development of frogs.

The northern red-legged frog (Rana aurora) is an amphibian found in the Pacific Northwest from Northern California to southwestern British Columbia, and its populations are declining in Oregon. They spend their early lives as tadpoles in ponds, then move into upland forests after metamorphosing into adults.

Researchers built runways to measure juvenile red-legged frog movement on land. ©Evan Bredeweg, Oregon State University

The researchers used tadpoles hatched from eggs gathered in the wild in Oregon in a series of small artificial ponds. To create a stressful environment, they reduced the water level of some ponds to about 20% of the starting level and left others at about the same level. The reduced water created higher maximum temperatures and lower minimum temperatures, left less area for the tadpoles to forage and led to more competition for resources.

They found that the water levels in the ponds had an effect on the size of the tadpoles after developing into frogs. “Animals in the permanent ponds were actually larger than the animals in the drier conditions,” Bredeweg said.

After the tadpoles developed, the researchers measured how quickly they moved up wet and dry runways made of topsoil to measure their movement behavior.

Smaller frogs, which were more often from the ponds with lower water levels, moved less quickly than those in high water. They were also slower to move from the get-go.

“In the wet environment, the animals were much more likely to move from the start,” Bredeweg said.

This lack of ability to move as much could have secondary impacts on a whole host of things important for survival. Frogs smaller in size and with less ability to move could be slower to escape from predators and might move shorter distances to find feeding or breeding opportunities.

Less movement might also mean they can’t move as far to find winter refuges and disperse to new areas in general.

These findings could have implications for the frogs under the changing climate.

“In the Pacific Northwest, the predictions for climate change is that there is going to be less summer precipitation and more precipitation during the winter,” Bredeweg said. If conditions are drier during key stages in tadpole development, it could mean whole populations of frogs are less physically fit and less able to survive the challenges of their environment.

But there is a positive side, Bredeweg said. The frogs managed to move even on the dry surfaces, which may be more common due to climate change. “Even in the face of dry conditions, they are still able to move,” he said.