New research examines the accuracy of information produced by citizen science apps for monitoring bird populations and found that it could actually offer a lot of utility for researchers, with some caveats.
The Wallis Annenberg Wildlife Crossing is a public-private partnership between the National Wildlife Federation and the California government. Other parties involved in the creation and construction of the project include the National Park Service and the city of Agoura Hills, California, where the crossing is located, according to the release.
Private donations made up 60% of the $90 million price tag, according to The Guardian, and the project is expected to open in early 2025. Caltrans, California’s Department of Transportation, will develop, build and maintain the crossing.
As conservationbiologists familiar with these clashing viewpoints, we wondered whether there was room for a more nuanced strategy than the typical yes/no standoff. In a recently published study, we used camera traps at hundreds of sites across Washington, D.C., to analyze the predatory behavior of urban free-roaming cats. The cameras recorded all cats that passed them, so our study did not distinguish between feral cats and pet cats roaming outdoors.
Our data showed that the cats were unlikely to prey on native wildlife, such as songbirds or small mammals, when they were farther than roughly 1,500 feet (500 meters) from a forested area, such as a park or wooded backyard. We also found that when cats were approximately 800 feet (250 meters) or farther from forest edges, they were more likely to prey on rats than on native wildlife.
Since the average urban domestic cat ranges over a small area – roughly 550 feet (170 meters), or one to two city blocks – the difference between a diet that consists exclusively of native species and one without any native prey can be experienced within a single cat’s range. Our findings suggest that focusing efforts on managing cat populations near forested areas may be a more effective conservation strategy than attempting to manage an entire city’s outdoor cat population.
Cats on the loose
Free-roaming cats are a common sight in Washington, D.C., which has a feline population of 200,000. Like many cities, Washington has had its share of cat management controversies.
Professionals on either side of the free-roaming cat debate largely agree that cats are safest when kept indoors. An outdoor cat’s lifespan generally peaks around 5 years, compared with 10 to 15 years for an indoor cat. Free-roaming cats face numerous threats, including vehicle collisions and contact with rat poison. Acknowledging these risks, most animal welfare organizations encourage an indoor-only lifestyle.
Similarly, there is little disagreement that cats hunt; for centuries humans have used them for rodent control. But invasive rats, which are often the target of modern rodent control, can grow too large to be easy prey for cats. In response, cats also pursue smaller species that are easier to catch. Studies have linked cats to 63 extinctions globally and estimated that cats kill 12.3 billion wild mammals annually in the U.S. alone.
Disagreements arise around handling cats that already live outside. Population management programs often utilize trap-neuter-return, or TNR – a process in which cats are trapped, spayed or neutered and re-released where they were caught.
In theory, TNR limits population growth by reducing the number of kittens that will be born. In reality it is rarely effective, since 75% of individual cats must be treated every year to reduce the population, which is often not feasible. Regardless, reproduction itself is not what most worries conservation biologists.
Today the Earth is losing wild species at such a rate that many scientists believe it is experiencing its sixth mass extinction. In this context, free-roaming cats’ effects on wildlife are a serious concern. Cats have an instinctual drive to hunt, even if they are fed by humans. Many wildlife populations are already struggling to survive in a rapidly changing world. Falling prey to a non-native species doesn’t help.
Since cats are generalist predators, their wild-caught diet tends to reflect the local species that are available. In areas with more birds than mammals, like New Zealand, birds are cats’ primary prey. Similarly, cat diets in the most developed portions of cities likely reflect the most available prey species – rats.
While cats top the list of harmful invasive species, rats aren’t far behind. In cities, rats spread disease, contaminate food and damage infrastructure. There aren’t many downsides to free-roaming cats preying on rats.
City centers have no shortage of rats, which can live anywhere, including parks, subways, sewers and buildings. But native animals tend to stay in or near areas with sufficient outdoor habitat, like parks and forested neighborhoods. When cats hunt in these same spaces, they are a threat to native wildlife. But if cats don’t share these spaces with native species, the risk declines dramatically.
Conservation funding is limited, so it’s critical to choose effective strategies. The traditional approach to cat management has largely consisted of attempting to prohibit cats from being loose altogether – an approach that’s incredibly unpopular with people who care for outdoor cats. Despite calls for outdoor cat bans, few have been enacted.
Instead, we suggest prioritizing areas where wildlife is most at risk. For example, cities could create “no cat zones” near urban habitats, which would forbid releasing trap-neuter-return cats in those areas and fine owners in those areas who let their cats roam outdoors.
In Washington, D.C., this would include forested neighborhoods like Palisades or Buena Vista, as well as homes near parks like Rock Creek. As we see it, this targeted approach would have more impact than citywide outdoor cat bans that are unpopular and difficult to enforce.
Hard-line policies have done little to reduce outdoor cat populations across the U.S. Instead, we believe a data-driven and targeted approach to cat management is a more effective way to protect wildlife.
Early on a cool June morning, heavy dew lies on the grass of rolling farm country somewhere in Tennessee, or Missouri, or Pennsylvania. Small patches of fog hang in low lying pockets of these fields. In the distance, hardworking farmers are starting their day. Farm equipment clangs, tractors roar to life and voices lining out the day’s work drift on the air.
This pastoral scene is repeated thousands of times each morning across rural America. But something is missing: the exuberant “Bob bob white!” call of the bobwhite quail that for generations was the soundtrack to summer mornings. Once abundant across the eastern U.S., bobwhite populations have declined by 85%. Calculations suggest that the remaining population could be cut in half within the next decade. [Listen to a recording of a Northern Bobwhite call]
Why is this happening? In a word, habitat. Native grasslands in the U.S., especially those east of the Great Plains, which once covered millions of acres, have almost completely disappeared. Some have been converted to croplands. Others have been allowed to grow back up into forests, where shade from the tree canopy prevents the growth of these grasses.
Still others have been planted with grasses that are native to Europe, Africa or Asia. These introduced grasses tend to be shorter than our tall, native species and grow in dense, solid mats that cover the ground. Native species, on the other hand, are bunchgrasses: They grow in clumps, with spaces between plants that benefit many of these nesting birds, especially the bobwhite.
Native grasses for birds, and cattle
One solution to these declines draws on the concept of working lands conservation – making agricultural lands productive not only for cattle, but also for declining species such as grassland birds. One compelling opportunity for such an approach is using some of the native grasses that have been lost from the eastern U.S. to provide pasture for cattle. Reintroducing these grasses to farms could benefit cattle farmers as well as birds. My new book, ““Native Grass Forages for the Eastern U.S.,” explains why and how these grasses can fit into working farms.
I have combined my research on native grasses over the past 15 years at the University of Tennessee Institute of Agriculture with the work of many other scientists that has accumulated over the past 100 years. Collectively, this research suggests that native grasses can not only be brought back but can play a strategic role on our farms today.
In the face of these stresses, I see native grasses like big bluestem as a promising solution. These grasses, which have grown in North America for millennia, are naturally well adapted to the eastern U.S., and I believe they can once again benefit family farms.
As I show in my book, these grasses have roots that can extend as much as 8 to 10 feet deep into the soil. They are remarkably drought tolerant and can grow and thrive in soils with low fertility and high acidity.
Their large root systems also help to increase the organic matter in soils, which makes the soil healthier and more productive. Building up organic matter, which consists mostly of carbon, stores carbon in the soil rather than the atmosphere.
But what about the cattle? Numerous studies show that forage yields are high for these species. Cattle readily consume them, and this diet produces strong gains on the growing animals. This combination of high yields, strong gains and low input requirements means that these forages can be produced profitably.
In that same study, we monitored the nesting success of two at-risk species associated with eastern pastures: grasshopper sparrows and field sparrows. We found that compared to pastures growing a nonnative grass species called tall fescue, the native grass pastures produced between two and six times more fledgling birds per acre. This is the outcome that working lands conservation seeks to deliver: more beef and more birds, all at a fair price.
Making the switch
The biggest challenge of cultivating native grasses is getting the grasses established. Converting existing pastures to native grasses requires completely renovating the fields, and lots of patience as the native grass seedlings develop. These species are slow starters.
Once they get a good root system under them, they can grow quite rapidly, but until then they are vulnerable to weed pressure. And converting fields is not cheap, due particularly to seed costs. However, farmers can receive financial support for planting native grasses from the U.S. Department of Agriculture’s Natural Resources Conservation Service.
As the world’s population grows, it will be a struggle to produce enough nutrient-dense proteins to feed everyone. Grasslands can produce high-quality dietary protein cost-effectively, while also reducing atmospheric carbon and supporting North American grassland birds and other wild species.
As King Solomon said long ago, there is nothing new under the sun. Native grasses are not new, but today I see them as a modern solution to some of our planet’s most pressing challenges.
A new fitness tracker that’s very much like a ‘Fitbit for fish’ is revealing new information about fish health and behavior. The first-of-its-kind device uses multiple sensors to wirelessly track what a fish experiences in real-time.
The device, a type of biosensor, can simultaneously collect data about a fish, including its location, heartbeat, tail movement, and burned calories, as well as the temperature, pressure, and magnetic field of its surrounding environment. This information can help scientists and managers understand the impact of climate change and infrastructure development on ecosystem health and, in turn, inform future management and conservation strategies.