Between a rock and a hard place: what happens when endangered species put each other in danger?

A guest blog by Kate Melanson

Imagine your favorite plant or animal. It can be your favorite because of you saw them in the wild and felt that they were your spirit animal, or because it plays a major part in its ecosystem, or just because it’s cool. Now think about what would happen if that favorite species were threatened with extinction. Imagine now that there is another species that eats your plant or animal that is also on the verge of extinction. What happens? Do you split them up? How would you do that? Do you save one and not the other? If so, which one? Who is qualified to make these decisions? Surely, you personally don’t have to decide. There has to be some sort of policy with very clear, specific wording to settle this. The truth is, though, there’s not.

The endangered species act, or ESA, was founded in 1973 and protects species that are threatened with extinction so that they may persist through our protection and conservation efforts. The ESA clearly states that we cannot protect one species at a cost to another. However, it does not provide any guidance regarding what to do when one threatened species threatens another. Without more precise guidance, decisions regarding these types of species interactions between two protected species are made on a case-by-case basis. Things get even more complicated when you consider other legislation and policies, such as the Marine Mammal Protection Act and the Migratory Bird Act, which might have conflicting advice.

Fitting a Channel Island fox with a shock collar was one solution to stop this protected species from feeding on Loggerhead shrikes (above). This is not a likely solution for sea otters and black abalone. Photos: iws.org and audubon.org

Fitting a Channel Island fox with a shock collar was one solution to stop this protected species from feeding on Loggerhead shrikes (above). This is not a likely solution for sea otters and black abalone. Photos: iws.org and audubon.org

One example of these challenging situations involves the Loggerhead Shrike, a species endemic to the California Channel Islands. At one point, the Loggerhead Shrike was one of the most endangered species of birds in America, partially due to the fact it was being eaten by the Channel Island Fox. The Channel Island Fox is also endemic to the islands and was put under protection by the government after being eaten by Golden Eagles. The solution: Foxes were fitted with shock collars so that if they came too close to the nests of Loggerhead Shrikes, they were shocked. This continued until the bird population recovered. There is currently still captive breeding of the shrikes on the islands, run through the San Diego Zoo.

Another example of a protected species interaction involves Caspian Terns in the Columbia River Basin, who were threatened because of the high vulnerability of nesting areas to human disturbances. Due to their population declines, Caspian Terns are now protected under the Migratory Bird Act. The problem is that Caspian Terns also eat salmon at a vulnerable stage in their life cycle. Salmon are protected by the ESA, which technically trumps the Migratory Bird Act, meaning salmon conservation takes priority over Caspian Tern protection. To rectify this, the entire flock of Caspian Terns in the Columbia River Basin was moved to an island farther from the river mouth to minimize their effects on salmon, in a somewhat controversial move.

A Caspian tern has a baby salmon in its mouth as it flies over the colony near the moth of the Columbia River. Photo: Columbian.org

A Caspian tern has a baby salmon in its mouth as it flies over the colony near the moth of the Columbia River. Photo: Columbian.org

For my dissertation, I am studying an unresolved interaction between black abalone and California sea otters in the Northern Channel Islands of California. Black abalone are listed as endangered under the ESA. They went through a mass mortality event caused by a disease that affects the abalone’s stomach, such that they essentially starve to death. Abalone attach to rocks using their stomach/foot. When they are weak from starvation, they fall off and die. This disease wiped out roughly 90% of the populations in some areas, and they still have not fully recovered.

Now what could sea otters have to do this? Sea otters are listed as threatened under the ESA. This was due to their being hunted to near extinction. Sea otters are now recovering and moving south from Central California to reestablish their historic range, including the Channel Islands. This is the same area where black abalone populations are still recovering. If sea otters move into the Channel Islands, the recovery of black abalone could be at risk. This brings us back to our policy conundrum. Both of these species are threatened and the law requires that we protect them both. But helping otters could put black abalone at a disadvantage. How can this be resolved?

A deep crack allows abalone to be protected from predators, such as otters that can’t reach within. An otter chows down on a black abalone. Photos: K. Melanson and D. A. Jessup (seaotters.com)

A deep crack allows abalone to be protected from predators, such as otters that can’t reach within. An otter chows down on a black abalone. Photos: K. Melanson and D. A. Jessup (seaotters.com)

Technically, abalone have the advantage in this situation because they are listed as endangered. This means that they are at a higher risk for extinction than otters, who are classified as threatened. As much as policy makers are able to take this into account to make unbiased decisions, it is likely that human emotion could influence policy as well. Many people have personal connections to widely beloved species such as otters, which can make it difficult to be impartial. Having an objective framework to solve this management issue and others like it will become increasingly necessary to maintain populations of species that can survive on their own.

As part of my dissertation, I will be trying to find all examples of conflicted species interactions involving threatened or protected species in scientific papers, judicial cases, and the public news. This will be used to determine what commonalities exist in the handling of these situations, what works, and to help provide guidance to managers and policy makers. Given how many species around the world are listed as at least threatened in some way, the number of options for how to manage these species interactions seem endless.

This figure provides some idea of how many species there are worldwide that are critically endangered (according to the IUCN), and the number of the species that could be affected by changing species interactions due to range shifts = all of them. Credit: IUCN

This figure provides some idea of how many species there are worldwide that are critically endangered (according to the IUCN), and the number of the species that could be affected by changing species interactions due to range shifts = all of them. Credit: IUCN

Kate Melanson is a PhD candidate in Ecology and Evolutionary Biology at UCSC.