Wildlife

Inbreeding in Orcas

Southern Resident killer whales, a small population of orcas living in the Pacific Ocean off the northwest coast of North America, are so isolated that they've taken to inbreeding, which has contributed to their decline, a new study finds. One reason for this decline is the group's limited geographic range, which stretches between British Columbia and Oregon.

In general, killer whales begin reproducing when they're 10 years old, hitting their reproductive prime in their early 20s. However, the Southern Resident orcas had less than half the chance of surviving through their prime years to reach 40, compared to the least inbred individuals. Additionally, females with the lowest level of inbreeding can expect to have 2.6 offspring in their lifetimes, while highly inbred females will have an average of 1.6 calves.

Monarch Decline

The number of endangered monarch butterflies that reached their winter habitat in the mountains of western Mexico dropped by 22% this season, the victims of illegal logging, habitat loss and climate change. The World Wildlife Fund Mexico reports that extreme 2022 temperatures in the United States contributed most to the decline.

Droughts, frosts and the loss of the migrating monarchs’ food source, milkweeds, across North America are also major factors. The monarchs once clustered in trees covering more than 18 hectares of forest in Michoacan state before logging, fires, drought and removal of sick or weak trees brought that number down to only around 2.5 hectares this year.