We just heard the news that a new killer whale baby was born into the L-pod of the critically endangered Southern Resident population. While we’re delighted to hear about the birth of a new killer whale calf, it’s important to be cautious. Unfortunately, newborn killer whales have a high mortality rate within their first six months. Scientists estimate it to be up to 50% (see ref below). This post will explain the challenges these young whales face in their early life stages.
Separation from their mothers
Killer whale calves rely on their mothers for food, protection, and social interaction, which greatly impacts their survival and development. If they separate from their mothers, their chances of survival are significantly affected. Newborn killer whales can become separated from their mothers due to various circumstances. They can include storms, the mother’s death or poor health, accidents or injuries, and human activities. One study in Germany from 2020 reported the loss of a killer whale calf and suspected the newborn was separated from its mother after a strong storm. It then got lost and stranded on the beach. Scientists performing the necropsy found that it still had milk in its stomach.
Prey availability and quality for their mother
Food is important for both the mother and the calf. If prey availability and quality are limited or decline, the mother may struggle to find sufficient food, which can lead to malnutrition and inadequate milk production. As a result, the killer whale calf may suffer from nutritional deficiencies, a weakened immune system, and stunted growth and development.
All the contaminants we have released into the ocean pose a severe threat to the health and well-being of killer whales. These pollutants, including heavy metals, pesticides, and flame retardants, enter the calves’ bodies primarily through their mother’s milk. The contaminants weaken the calves’ immune response, making them more vulnerable to diseases. They also disrupt their development, leading to future reproductive issues and reduced fertility. The accumulation of these pollutants can have long-term consequences for the survival and sustainability of killer whale populations.
As if it was not enough, baby killer whales also have to deal with underwater noise from shipping, fishing, recreational boating, or naval exercises. Excessive noise disrupts their communication and echolocation abilities, which are essential for survival. It disrupts the natural acoustic environment they rely on, causing stress and potentially leading to behavioral changes or isolation from their pod members.
Entanglement and collisions
Speaking of boats and fishing, these young calves can get caught in nets or lines, resulting in injuries, restricted mobility, or even death. Additionally, collisions with boats can cause severe harm or even be fatal. Due to their limited awareness and slower reaction times, newborns are particularly vulnerable to these incidents. We can reduce these two threats (noise, as well as entanglements/collisions) through the implementation of strict speed limits for all vessels.
Threats from conspecifics
In 2018, Jared Towers et al. reported a case of infanticide, where an adult male killer whale and his own mother targeted and killed a newborn calf from their population (Transient killer whales). It was the first time scientists observed a male and its mother kill an infant in the marine mammal realm. Although very rare, this type of event is a reminder that there is still so much to learn about how these animals interact with one another.
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Sources and further reading
- Olesiuk, Peter F., Michael A. Bigg, and Graeme M. Ellis. “Life history and population dynamics of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State.” Report of the International Whaling Commission, Special 12 (1990): 209-243.
- Schnitzler, Joseph G., et al. “Supporting evidence for PCB pollution threatening global killer whale population.” Aquatic toxicology 206 (2019): 102-104.
- Towers, Jared R., et al. “Infanticide in a mammal-eating killer whale population.” Scientific Reports 8.1 (2018): 4366.
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