They're big and powerful, but humpback whales are no match against tiny parasites with voracious appetites hitching a ride on their bodies.
Whale lice from the species Cyamus boopis live exclusively on humpback whales.
Close-up images of the pale parasites were captured on a calf with its mother off Queensland's Hervey Bay a week ago as they migrated towards the Southern Ocean.
"They all have them. The adults have the whale lice and the little ones too," said tour boat operator Peter Lynch.
"They just live on the whale and get a free ride, eating bits of dead skin."
Mr Lynch said the size of a lice population on a whale was a good indicator of the health of the animal.
"When you do get a very sick or injured humpback whale and its swimming slows down, that whale lice population explodes," he said.
"We have seen unfortunately in the past, a very sick humpback come into the bay and it had a pink colouration appearance … its entire body was covered in whale lice."
The whale louse is an ectoparasitic crustacean, meaning it lives on the outside of its host and usually only measures a few millimetres in length.
University of Sunshine Coast ecologist Alexis Levengood says the only way a whale becomes infested with lice is through body contact with another whale.
"You can study the lice of the whales and find out who a whale has been interacting with," Dr Levengood said.
"They usually get them through mating or from aggression and if they're fighting.
"The lice cannot live free flowing in the ocean. They have to be attached to an individual and reproduce on that animal."
Hitching a lift
Whale lice are considered regular commuters on the marine mammals, which has led to theories about how they affect whale behaviour.
"If they're near the eye, near the blowhole openings – what might be considered more delicate parts of the body – that could be another reason for some of the splashing activities at the surface, maybe to try and dislodge the ones that are annoying them," Mr Lynch said.
"It really is kind of icky to think that the outside of [their] body is one huge, moving, live mass."
Dr Levengood said the scientific jury was still out on whales' breaching behaviour.
"I know there is a lot of speculation around why humpbacks breach the water's surface," she said.
"There's a lot of theories and no real conclusive evidence on why they do this."
Dr Levengood said the lice played an important role in controlling algae on whales' bodies.
"It's a nice thing for the whale to not have algae on them and for the lice to eat the flaking skin off the whale and those open wound areas," she said.
"They can cause minor skin damage, but it does not lead to significant illnesses."
