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'Keep distance from sea animals': Seal attacks linked to Domoic acid poisoning

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There is a reason why Hollywood hasn’t yet made a horror movie about a menacing seal running amok. Recent events notwithstanding, reports of seal attacks rarely make the headlines.

Perhaps this is the reason why a video clip showing a seal pup chasing and biting a child and a woman in the swash at Clifton Fourth Beach earlier this month went viral.

Capetonians also sat up when the media reported on a seal attack at Fish Hoek Beach.

During this incident, which took place over the Heritage Day weekend in September last year, Katharine Liese was chased by a seal that grabbed her by the leg.

On Wednesday January 4, a day after the attack at Clifton Fourth Beach, the NSRI also stated that their reports indicated similar incidents involving aggressive seals in Hout Bay, Yzerfontein and Noordhoek.

Brett Glasby, wildlife management programme coordinator at Two Oceans Aquarium, says the behaviour exhibited by these seals in recent months is very far from normal.

“I have been rescuing seals on Cape Town beaches for 14 years and have never experienced this kind of behaviour. Normally, when seals are encountered and feel harassed, then they return to the water and escape. Animals that are weak or sick and unable to escape sadly die from the stress of human interaction.”

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According to Glasby, the most likely cause of this uncharacteristic behaviour is Domoic acid poisoning. He explains this happens when animals feed within a red tide bloom. He says the poisoning causes swelling around the brain and heart.

“This normally results in death but if the poisoned animal survives, it is likely to suffer lifelong side effects. The primary side effects are a weaker heart and neurological symptoms.”

From the end of 2021 to the beginning of last year, marine wildlife experts noted a mass death event that originated on the West Coast.

Glasby says this event was due to Domoic acid poisoning.

“We also know from similar events that have been documented in California and New Zealand that for roughly 18 months after the event, some seals will exhibit unusual behaviours, predominantly excessively aggressive defensiveness. This means that their response to stress or a possible stress is to respond aggressively.”

According to what Gatsby and his team have seen and what was recorded internationally, the neurological side effects appear to remove the flight portion of the fight or flight response to stress.

“This means that when these animals feel threatened, they respond by fighting as opposed to escaping the situation.”

He adds that there is absolutely no way to know how many seals are afflicted. His team has also not been able to fully assess which other marine species are affected, but he says, from international data, they know that dolphins and whales are also affected.

It is also known that animals with this kind of brain damage are likely to have a shorter than usual lifespan.

“All animals have a fight/flight response to a threat for a reason. The first option should always be to avoid danger and escape, if that is not possible then fight to survive. Realistically, an animal that does not avoid danger and chooses to face all dangers head-on will result in the death of the animal very quickly,” explains Glasby.

As to how much damage an affected seal can inflict on a human body, he says a seal bite is a serious injury.

“The primary trauma will result in puncture wounds, bruising and deep tissue trauma. The secondary effect is very possibly bacterial infections. Seals have a very high bacteria load in their mouth and this can lead to a very bad infection. If bitten, seek medical attention.”

He concludes it is vitally important that members of the public treat all wild animals with respect and give them a wide berth.

“Keep your distance from seals on the beach, if the animal does not feel threatened then there is no reason for it to respond aggressively.”

  • In case of any injured, hurt, or coastal wildlife in distress, contact the City of Cape Town on 021 480 7700 from a cellphone, or 107 from a landline. The appropriate response will be initiated to assist the animal. Members of the public are urged not to act on their own and without authority.


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