Artifacts: Scavengers

How do you tell a lesion or injury from damage done by scavenging? Even before an animal hits the beach scavenging by everything from sharks to birds to the neighborhood dog may cause damage to the carcass. While this is nature’s best recycling program, it can be difficult at times to tell normal scavenging from pre-mortem injury or pathological lesions.

Some of the most common patterns to look for include:

sharkThis animal has a shark bite as well as bird scavenging and damage from rolling around on sand.

Sharks – shark scavenging can range from obvious great while shark or other large shark bites with the classic half moon shape to smaller more oval shaped bites made by cookie cutter sharks. To determine whether the wound was pre or postmortem examine the edges of the bite and look for signs of hemorrhage. Most of the time these wounds will be postmortem – luckily for the animal!

Birds – birds are usually one of the first and most aggressive large scavengers that will arrive at a fresh carcass. Sometimes birds have even been observed attacking a freshly stranded live animal before it has died on the beach. Classic signs of bird scavenging include missing eyes, enlarged uneven holes in and around the eye sockets, a large hole with uneven edges at the caudal margin of the lower jaw in cetaceans where the pan fat pad is located (an especially tasty treat for birds), and enlargement of the genital and anal openings. In cetaceans, birds will also begin eating around the blowhole as well.

Small Carnivores – The extent of small carnivore predation will vary by area but may include bite marks. Also look for paw prints around the carcass.

Dogs – Dogs most often roll on carcasses (often at the utter dismay of their owners) and may also bite or tear at the carcass.

Humans – Humans can be scavengers too! Beach goers may collect “souvenirs” from animals. Look for smooth-edged cuts indicating that a knife may have been used. Remember – even taking souvenirs from a dead marine mammal is against the law and is considered human interaction. It should be noted in the comments of the Level A form what was observed.

A special note about missing heads!

Most stranding programs frequently get calls from the public about carcasses that appear to have been beheaded! Certainly this can be distressing for someone that has not seen this before. Experienced stranding personnel will know however that 9 times out of 10 the head has been lost through scavenging, usually while still at sea. The skull is a heavy bone and in contrast to the rest of the body will often times sink in the water column. The joint between the skull and the cervical vertebrae is actually quite fragile and after a few days of scavenging by fish and birds the skull may be fully removed from the rest of the body.

QUICK TIP: Look for jagged edges and lack of hemorrhage around the neck to distinguish between normal scavenging and potential human interaction.

The following photo gallery gives examples in both pinnipeds and cetaceans of some of the hallmark patterns made by large scavengers.  CLICK on an image to see an enlarged view.