Elephant seals have genetic scars from intense hunting

An international research team has explored the profound genetic impact of hunting on northern elephant seals. The experts found genetic scars in the animals, which were once hunted to near extinction.

The findings of the study, published in the journal Nature Ecology and Evolution , reveal that these genetic effects have persisted for many decades after the seals barely escaped extinction.

Elephant seals on brink of extinction

At the turn of the 20th century, northern elephant seals were nearly wiped out by hunting, with their numbers dwindling perilously.

The experts noted that extensive hunting by commercial sealers between 1810 and 1860 largely eliminated the northern elephant seal from most of its geographical range, and it was considered extinct by the 1890s.

"Genetic analyses suggest that the population was likely reduced to fewer than 25 animals at that time," explained Dr Joseph Hoffman, lead author of the study and head of the Evolutionary Population Genetics group at Bielefeld University .

Such dire population declines can strip a species of its genetic diversity, amplifying the risk of inbreeding and jeopardizing survival. A bright ray of hope in this grim tale, however, is the recovery of the northern elephant seals.

Despite the odds, the population has bounced back to around 225,000 individuals by 2010. How did this near-extinction event impact their genetic diversity and health? The study offers fascinating revelations.

Beyond extinction: Survival cost for seals

The team used a sophisticated approach for the investigation, fusing genetic data, health records, population size modeling, and genetic simulations.

According to the findings, the intense population decline led to both useful and harmful genes being wiped out from the northern elephant seal's gene pool. These effects were not witnessed in their southern elephant seal counterparts who avoided such a dramatic decline .

"The highly reduced genetic diversity, including the loss of beneficial gene copies, may impair the ability of northern elephant seals to cope with future environmental changes, including those caused by anthropogenic climate change, changes to the species’ habitat, or even natural threats such as disease outbreaks," said study senior author Dr. Kanchon K. Dasmahapatra.

Harmful mutations from population decline

Every species carries some harmful mutations, hidden away, but inbred individuals might unveil these health threats.

The team scrutinized key health traits, like body weight, blubber thickness, and disease susceptibility.

"To our surprise, we found no signs of health problems related to inbreeding. We believe the severe population decline may have eliminated many harmful mutations," said Dr. Hoffman.

"Our study illustrates how a species' unique population history shapes its genetic diversity," noted Dr. Dasmahapatra.

"Each species responds differently to threats, so individualized approaches are essential," said Dr. Hoffman.

Saving seals from extinction

The findings from this study have far-reaching implications in the field of conservation genetics. The northern elephant seal serves as a pivotal case study on the genetic consequences of population bottlenecks.

By understanding the effects of reduced genetic diversity, conservationists can derive insights into how other species might fare under similar threats.

"Understanding the genetic and fitness consequences of anthropogenic bottlenecks is crucial for biodiversity conservation. However, studies of bottlenecked populations combining genomic approaches with fitness data are rare," noted the researchers.

This knowledge is essential in formulating strategies that not only aim to preserve existing genetic diversity but also foster resilience in the face of future challenges.

Bridging science and policy

In light of the study's revelations, there is an urgent need to bridge the gap between scientific research and policy-making. Effective conservation strategies require a symbiosis between empirical evidence and regulatory frameworks.

Policymakers must account for genetic factors when devising conservation policies , ensuring that the efforts to restore or protect species are both scientifically grounded and pragmatically feasible.

This integration of science and policy could pave the way for innovative, adaptive management practices that strengthen the resilience of biologically diverse ecosystems, safeguarding them for future generations.

"The northern elephant seal provides a compelling opportunity to investigate the complex interplay between population declines, genetic load dynamics, and fitness," wrote the study authors.

"The northern elephant seal is a classic example of a wild vertebrate that is believed to have purged at least part of its genetic load as a result of a severe bottleneck."

The study is published in the journal Nature Ecology & Evolution .

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