December 4, 2025 — The right whale calving season begins in mid-November and runs through mid-April. Researchers have identified one calf so far this calving season.
Every single female North Atlantic right whale and calf are vital to this endangered species’ recovery. Since 2017, the whales have been experiencing an Unusual Mortality Event, which has resulted in more than 20 percent of the population being sick, injured, or killed. The primary causes of the Unusual Mortality Event are entanglements in fishing gear and collisions with boats and ships. In the last decade, there have been more North Atlantic right whale deaths than births.
Reproductive females are producing fewer calves each year, which impacts the ability of the species to recover. Female right whales become sexually mature at about age 10. They give birth to a single calf after a pregnancy lasting over a year. Three to four years is considered a normal or healthy interval between right whale births. But now, on average, they are having calves every 7 to 10 years. Biologists believe the additional stress from entanglements, vessel strike injuries, and changes in prey availability due to climate change all likely contribute to right whales calving less often.
With the current number of females and the necessary resting time between births, 20 newborns in a calving season would be considered a relatively productive year. However, given the estimated rate of human-caused mortality and serious injury, we need approximately 50 or more calves per year for many years to stop the decline and allow for recovery. The only solution is to significantly reduce human-caused mortality and injuries, as well as stressors on reproduction.