Pinnipeds are a group of carnivorous marine mammals, and although well adapted to life in the ocean, these animals need land or sea ice to rest and complete important life history events like pupping and molting. Alaska is home to several species of pinniped ranging from walruses to seals and sea lions, with some of my favorites being northern fur seals and ribbon seals.
Northern fur seal, one of Kyle's favorite pinnipeds. Image Source
The Arctic environment is undergoing changes as rising temperatures are reducing the quality and extent of sea ice. As mentioned above, sea ice is an important substrate for resting pinnipeds. If sea ice continues to recede, then this substrate may be located farther away from a pinniped’s preferred foraging grounds, potentially forcing animals to change their foraging behavior and/or travel greater distances in search of food. In addition, the melting of sea ice may have large impacts on food availability, as many fish rely on the cold and stable environment that Arctic sea ice provides.
I am interested in understanding how Alaska’s pinnipeds may be adapting to these ecosystem changes. To investigate this question, I’ll be looking at Time-Depth Recorder (TDR) data collected by collaborators at NOAA from a suite of Alaskan pinnipeds. These tags are glued to the upper back or neck of a pinniped and collect information including……..time and depth of dives amongst some other things. If animals are not recaptured to collect the tag after a deployment period, the TDR tag will simply fall off when the animal sheds its fur during its annual molt. This non-invasive method is a great way to learn more about Alaska's marine mammals.
A ribbon seal with TDR tag glued to its head. Image from NOAA's ice seal research program.
TDR data allows me to parse out key physiological boundaries and determine how closely seals or sea lions are operating to them. One constraint that I am particularly interested in is the aerobic dive limit (ADL). This boundary is the amount of time a pinniped can spend underwater before their metabolism switches from mainly aerobic to anaerobic pathways. Anaerobic metabolism is inefficient, costs more energy, and produces lactic acid as a byproduct (this is what makes your muscles burn in a tough workout). If pinnipeds exceed this limit on dives often, there may be adverse effects. However, many pinnipeds exhibit great flexibility with this boundary, diving well beyond the ADL, and I’d like to learn how Alaskan pinnipeds may be using this flexibility in adapting to climate change.
This spring, I will be participating in an ice seal research cruise with NOAA’s Marine Mammal Laboratory. For 6 weeks, we will follow the sea ice and deploy tags on seals we catch while also measuring body conditions and completing other health assessments. Stay tuned for more updates about my research in the Arctic!
Written by: Kyle Kolda