A stressful environment can prevent humans from thriving and that can now be said of shark pups too.
An international team of researchers including Dr. Jodie Rummer from the ARC Centre of Excellence for Coral Reef Studies at James Cook University, found shark pups raised in environments that are hurt by climate change and other human-induced stressors fail to thrive compared to those shark pups in areas untouched by humans.
Sharks pups in one group had to deal with human-induced stressors
The study compared the foraging and conditions of two populations of newborn reef sharks with one group in St. Joseph, an uninhabited, remote, small atoll located in the outer islands of Seychelles. There have been no environmental changes in that area. The other group was in Moorea, French Polynesia, the popular tourist destination that had lost as much of 95% of its live coral in a five year period before the study commenced. The study lasted four years and looked at 546 young sharks that were captured.
The researchers found the shark pups that were born bigger and heavier in Moorea compared to their St. Joseph counterparts quickly lost their physical advantages over the St. Joseph shark pups.
“We found that although shark pups are born larger, heavier and better conditioned in Moorea, they soon lost their physical advantage over the pups in St Joseph,” Dr. Rummer said. “Bigger mothers give birth to bigger babies, which is what happens in Moorea. But that doesn’t necessarily mean the babies will eat and grow quickly after that.”
Moorea shark pups began foraging later in life
The scientists found the larger pups from Moorea started foraging for food later than the pups in St. Joseph which resulted in the decline in the condition of their bodies. The smaller pups from St. Joseph became much more successful predators as they began foraging at a younger age.
The scientists believe the Moorea shark pups were at a disadvantage because the quality and quantity of prey to feast on has degraded over the years. That was in addition to stressors brought on by humans including over-fishing, climate change and the development of buildings and homes on coasts.
“Sharks are at risk from human-induced stressors because they may not be able to adapt fast enough to keep pace with the changes that are happening in their environment,” Dr. Rummer said. “They are slow growers and take a long time to reach sexual maturity. When they do reach sexual maturity, they only have a few babies. Even fewer survive."