The curious case of the disappearing snakes

Date:

Share post:

The loss of any species is devastating. However, the decline or extinction of one species can trigger an avalanche within an ecosystem, wiping out many species in the process. When biodiversity losses cause cascading effects within a region, they can eliminate many data-deficient species ¬- animals that have eluded scientific study or haven’t been researched enough to understand how best to conserve them.

The curious case of the disappearing snakes
An MSU-led study featured on the cover of this week’s Science magazine should
sound alarm bells regarding the “biodiversity crisis” or the loss of wildlife
around the world [Credit: Andrew Hein]

“Some species that are rare or hard to detect may be declining so quickly that we might not ever know that we’re losing them,” said Elise Zipkin, MSU integrative biologist and the study’s lead author. “In fact, this study is less about snakes and more about the general loss of biodiversity and its consequences.”

The snakes in question reside in a protected area near El Copé, Panama. The new study documents how the snake community plummeted after an invasive fungal pathogen wiped out most of the area’s frogs, a primary food source. Thanks to the University of Maryland’s long-term study tracking amphibians and reptiles, the team had seven years of data on the snake community before the loss of frogs and six years of data afterwards.

Yet even with that extensive dataset, many species were detected so infrequently that traditional analysis methods were impossible. To say that these snakes are highly elusive or rare would be an understatement. Of the 36 snake species observed during the study, 12 were detected only once and five species were detected twice.




“We need to reframe the question and accept that with data-deficient species, we won’t often be able to assess population changes with high levels of certainty,” Zipkin said. “Instead, we need to look at the probability that this snake community is worse off now than it used to be.”

Using this approach, the team, which included former MSU integrative biologists Grace DiRenzo and Sam Rossman, built statistical models focused on estimating the probability that snake diversity metrics changed after the loss of amphibians, rather than trying to estimate the absolute number of species in the area, which is inherently difficult because snakes are so rare.

“We estimated an 85% probability that there are fewer snake species than there were before the amphibians declined,” Zipkin said. “We also estimated high probabilities that the occurrence rates and body conditions of many of the individual snake species were lower after the loss of amphibians, despite no other systematic changes to the environment.”




When animals die off en masse, such as what is happening with amphibians worldwide, researchers are dealing mainly with that discovery and are focused on determining the causes. But what happens to everything else that relies on those animals? Scientists don’t often have accurate counts and observations of the other species in those ecosystems, leaving them guessing to the consequences of these changes. The challenge is exacerbated, of course, when it involves rare and data-deficient species.

“Because there will never be a ton of data, we can’t pinpoint exactly why some snake species declined while others seemed to do okay or even prospered after the catastrophic loss of amphibians.” Zipkin said. “But this phenomenon, in which a disturbance event indirectly produces a large number of ‘losers’ but also a few ‘winners,’ is increasingly common and leads to worldwide biotic homogenization, or the process of formally dissimilar ecosystems gradually becoming more similar.”

The inability to put their finger on the exact cause, however, isn’t the worst news to come from their results. The truly bad news is that the level of devastation portends to much greater worldwide loss than the scientific community has been estimating.




“The huge die-off of frogs is an even bigger problem than we thought,” said Doug Levey, a program director in the National Science Foundation’s Division of Environmental Biology. “Frogs’ disappearance has had cascading effects in tropical food chains. This study reveals the importance of basic, long-term data. When these scientists started counting snakes in a rainforest, they had no idea what they’d eventually discover.”

Zipkin agrees that long-term data is important to help stakeholders ascertain the extent of the issue.

“We have this unique dataset and we have found a clever way to estimate declines in rare species,” she said. “It’s sad, however, that the biodiversity crisis is probably worse than we thought because there are so many data-deficient species that we’ll never be able to assess.”

On a positive note, the scientists believe that improved forecasts and modeling could lead to bolstering conservation efforts. Making data-driven, proactive changes can prevent massive die offs and curb biodiversity loss.

The study is published in Science.

Source: Michigan State University [February 13, 2020]

ADVERTISEMENT

spot_img

Related articles

Increased tropical forest growth could release carbon from the soil

A new study shows that as climate change enhances tree growth in tropical forests, the resulting increase in...

Climate change to profoundly alter Great Lakes region

Intense rainstorms, floods and heat waves will become more common in the Great Lakes region due to climate...

A new study to improve seabird conservation in Patagonian ecosystems

Preserving a 300,000 square km area in Patagonian waters could improve the conservation of 20 % of the...

India, South Africa and Australia shared similar volcanic activity 3.5 billion years ago

Cratons are pieces of ancient continents that formed several billions of years ago. Their study provides a window...

Fossil forests under Antarctic ice

In around 1833 the first specimens of fossilized wood from Antarctica were reported by surgeon, naturalist and artist...

An underestimated threat: Land-based pollution with microplastics

Tiny plastic particles also present a threat to creatures on land and may have damaging effects similar or...

Earth’s ‘solid’ inner core may contain both mushy and hard iron

3,200 miles beneath Earth's surface lies the inner core, a ball-shaped mass of mostly iron that is responsible...

First comprehensive map of geology beneath the East Antarctic Ice Sheet

An international research team has generated the first comprehensive map of geology beneath the East Antarctic Ice Sheet...