Published 14:01 IST, January 31st 2021
Arctic seals lose body mass at alarming rates due to climate change, say researchers
NOAA Fisheries study found that three species of Arctic seals are experiencing impacts of climate change and they are losing body mass at alarming rates.
A recent National Oceanic and Atmospheric Administration (NOAA) Fisheries study found that three species of Arctic seals are experiencing impacts of climate change and they are losing body mass at alarming rates. As per the study, the researchers studied ribbon, spotted and harbor seals in the Bering Sea and the Aleutian Islands from 2007 to 2018. They tracked the changes in how heavy seals were in relation to their length and found that the seals’ body condition declined in almost all age and sex classes in every studied species.
The researchers noted that the aforementioned three species are all typically resilient, long-lived predators that eat at a variety of prey. They also informed that only two groups, spotted seal subadults and adults, did not experience a decline in body condition. Lead researcher Peter Boveng said that the findings point strongly to climate-related impacts. He also added that the team saw declines in seal condition that coincided with recent pronounced warming.
Boveng said, “Warming conditions in the Arctic seem to be affecting the condition of individual seals in a way that could impact their populations”.
According to the study, the researchers said that for ribbon and spotted seals, the decline in body conditions is likely related to their reliance on ice environment during pregnancy and nursing cycles. They noted that the species usually gather near the edge of sea ice in the spring to give birth between April and May, and mothers have “very high energy needs during this time. The researchers said that they where they gather in the Bering Sea has historically had plenty of food available for that time, however, throughout the study period, sea ice decreased, forcing the mothers to search for food in areas that may have been less favourable.
Climate-related impact
The study noted that an average-sized individual seal saw a decrease in body composition of roughly 13 pounds a year. Male harbour seals weigh about 265 pounds on average, and the female weighs about 220 pounds. Further, the study also noted that the Aleutian Islands population of harbor seals have undergone a “long-term decline” between 1980 and 1999 when the population dropped by 86 per cent. However, the researchers also said that they do not think that decline is linked to the lower body condition.
Boveng explained, “We suspect that the recent declines in body condition during our study are an acute response to the very strong North Pacific marine heatwave, rather than a continued chronic response to whatever has caused the long-term decline in numbers”.
Further, the authors of the study noted that climate change has been shown to impact fish and other animals low on the food chain who are less able to switch between sources of prey as ecosystems change. However, the also added that when animals like ribbon, spotted and harbor seals are facing physical decline, it likely reflects broad underlying ecological shifts in multiple prey species.
During the time of the study, there were two unusual mortality events in Alaska that impacted all of the ice seals in the area, including the ribbon and spotted seals. The first event revealed seals having sores, hair loss and lethargic behaviour, but in good nutritional condition. In the second event, large numbers of bearded ringed and spotted seals, most of which were young or emaciated, were found stranded or dead. This mass mortality, researchers said, "strongly suggests a climate-related impact".
Updated 14:01 IST, January 31st 2021