Gulls That Eat Whales Alive
By Roger Payne
The photo above by Judith Scott of WhaleWatchSA.com shows a cape gull biting into the skin of on a South African, Southern Right Whale’s back—a behavior not previously reported in South African waters, though southern right whales are well studied in South African waters.
It is the same behavior we first observed in 1980 from kelp gulls in the waters of Argentina’s Península Valdés. Scott’s photo demonstrates that it has recently appeared on the opposite side of the South Atlantic.
Kelp gull, Cape gull and Dominican gull are different names for the same species (Larus dominicanus). It is the southern hemisphere equivalent of the northern hemisphere’s black-backed gull (Larus fuscus) the world‘s largest gull. Kelp gulls are so similar to black-backed gulls they have sometimes been considered a subspecies of black-backs.
Feeding on live whales doesn’t seem to be a matter of one-trial learning for these gulls. Perhaps it takes them a long time to build up enough courage to feed on the skin of a live right whale. Such caution is a good idea; a killer whale has been seen, on the outer coast of Península Valdés, striking with its tail at a gull that pecked it, and though that gull narrowly escaped, the stomach contents of killer whales often include the toenails of several gulls. It seems right that even though biting pieces out of live right whales has been going on in the Península Valdés population since the 1980s the behavior took months and years to reach its current frequency. So where did the South African kelp gulls learn this behavior? One possibility could be by watching western, South Atlantic kelp gulls in an area where western and eastern populations overlap.
The excellent map by T.D. Smith, et al of the distribution of the whales that were seen and killed during the days of sail, between 1780 and 1920, shows a band of right whale captures and sightings running roughly from east to west across the South Atlantic between Península Valdés and South Africa. It strongly suggests that southern right whales once occupied the waters of those latitudes all the way from South America to South Africa and beyond. But in modern times although both Península Valdés and South Africa host large populations of southern right whales, no one has reported a known South African right whale in Valdés, or a known Valdés right whale in South Africa.
The islands of Tristan da Cunha and Gough lie about halfway between South Africa and Valdés, and South African right whales have occasionally been seen there, as have Valdés right whales.
Is the same pattern true of kelp gulls? It would be interesting to know the home ranges of kelp gulls, and how far from their nesting colonies they venture. The Avibase bird checklist classifies the present status of kelp gulls in Tristan da Cunha as “Rare/Accidental.” This suggests that it is probably not a place where western and eastern kelp gulls learn new behaviors from each other if all gulls must see this behavior several times before daring to feed on live right whales. (Orcas are omnipresent and it seems likely that South African gulls are aware that it is not safe to feed on them.) Adoption of the behavior would require gulls from both sides of the Atlantic to be present on the same days, during the same period that right whales are present, and in several days of good weather (on rough days waves breaking over the backs of whales reduces the frequency of gull attacks). These requirements suggest that the behavior photographed by Scott may constitute an independent discovery by an eastern south Atlantic kelp gull. If I am wrong and the behavior was an import from Península Valdés it suggests that once a new behavior has gained wide acceptance in a population, it can jump even to distant populations.
At Valdés, mussels are the preferred food of kelp gulls (there are fewer attacks on whales at low tide, when mussels are available to gulls, than at high tide when they are not). At present the population of kelp gulls around Península Valdés is abnormally high, and it is likely that feeding on right whale skin constitutes a significant proportion of the Valdés kelp gull diet.
When this behavior began, most gull attacks were on adult whales but the adults have since learned how to raise just their heads to breathe and their heads are covered with callosities which are probably too fibrous and tough for a gull to be able to carve off a piece with its bill. However newborn calves have to breathe on average once every 20 seconds and it takes them much of their first season to learn how to catch breaths in a way that avoids being attacked. As a result, it is the calves that are the principle focus of gull attacks (calf skin is also presumably tenderer then the skin of adults).
Right whales are accessible to gulls around Península Valdés because the waters there are so shallow that when swimming underwater a Right Whale can usually be seen from above by a flying gull. So the gulls just follow them from one surfacing to the next. If the whales swam deeper, the gulls would be unable to see them well enough to follow. However, in the areas of the Valdés bays much frequented by Right Whales, the water is too shallow and often too clear for a Right Whale to get deep enough to be invisible from above. They also have a preference for staying in shallow water most of the time with other mothers nearby as a protection and herding mechanism.
Gulls are seldom seen very far from shore so another way right whales could avoid them is to take up residence further offshore than kelp gulls are found. That might even explain, in part, why western, North Atlantic right whale mothers don’t keep their newborn young near shore even though we know from watching southern right whales that hugging the coast offers right whale mothers a major advantage if their calves are attacked by killer whales. Valdés right whale mothers keep their calf as close as possible to the shore, and when orcas attack a mother/calf duo, the mother interposes her body between her calf and the approaching orca. This pushes the calf into water too shallow for the orca to attack it from below. Also, orcas can’t maneuver as freely in very shallow water. If a group of orcas press the attack the mother cocks her tail sideways—a threat that is clearly understood by the orcas, for they leave immediately. Right whales are tail fighters. Their tails are deadly weapons when slashed laterally (a behavior that the long-tailed, vegetarian dinosaurs are believed to have practiced).
From these observations, one begins to suspect that gulls may have a much larger effect in shaping the lives of whales than that for which they have hitherto been given credit. It seems likely that over the years, gulls, and perhaps other seabird species too, must have learned to feed from more than one species of baleen whale. The most vulnerable would be those that spend the longest times at the surface. Besides right whales, this includes, at least, bowheads, gray whales, humpbacks, and sperm whales. (The rorquals are largely out of the running as they usually spend very little time at the surface—not enough to give a gull long enough to approach, descend, land, and bite out a piece of flesh.)
Sperm whales aren’t attacked because they dive for periods of an hour or more, are seldom seen near shore, and usually dive so deep they can‘t be followed from above, even when in the clearest, mid-ocean water. However, because gulls seldom fly more than a few miles off shore, all whale species are safe from their attacks if they stay beyond that distance. However, when farther offshore, right whales face a problem from orcas, because offshore almost always means deep water wherein any whale species is more vulnerable to orca attacks.
It is possible that bird attacks may explain the former absence of humpback whales around Hawaii. Currently, Hawaiian waters are one of the main winter destinations of North Pacific humpback whales. Yet humpback whales were almost never reported by the crews of the Arctic bowhead whaling fleet that overwintered in Hawaii in the 19th century, even though they anchored in what is now an area off Maui where you can hardly look out to sea in winter and early spring without seeing humpback whale blows. This suggests that humpback whales may appear and disappear from particular coasts over the years, just as right whales are known to do. But what is the cause? Back in the time of the Arctic bowhead hunt, humpbacks were not yet the main quarry of whalers, and it is unlikely that hunting was responsible for causing populations of Pacific humpbacks to move around. Their baleen is of little value, they swim too fast to catch easily, and killing them is particularly dangerous (as a Norwegian whaler famously put it when whaling was done from small boats: “I do not like to kill the humpback; No. No. No. No. No.”).
It seems much more likely that bowhead whales would attract gull attacks, because bowheads spend most of the year near shore and black-backed gulls have a circumpolar distribution. I have always been impressed by how similar to right whale behavior bowhead whale behavior is. It is possible that one of the advantages bowheads gain from never taking more than short sorties out of pack ice into pack ice-free waters is that the pack ice offers protection from above against bird attacks. The ice could enable them to stay in water that provides abundant nutrition without the gulls driving them into more marginal, lower latitude habitats where they would have to compete with right whales.
In pack ice bowheads can follow each other underwater (by some as yet unknown, non-visual technique) from one breathing hole to the next, but presumably an above-water observer like a gull would find if all but impossible to follow them in pack ice. To a gull that is looking for signs of life in moving ice, bowheads will appear in an unpredictable spot, take a few breaths and vanish. The gulls cannot follow the whale to the next breathing place, the way they can in Valdés where they just laze in the water next to a whale or make brief flights above a submerged right whale waiting for it to surface for a breath and then attack. Gulls might watch and learn where a breathing gap is in pack ice by seeing blows there from a bowhead, but the bowheads can easily avoid gulls by using different breathing holes for the next breath. The holes are much less visible from above than from below, because from below they are the best illuminated features, whereas from above breathing holes are just another one of thousands of dark spots that may or may not be deep enough to go all the way through the surface ice to below it.
One imagines that right whales endure gull attacks as long as they can and then set out in search of a gull-free area, or an area where no living gulls have seen other gulls bite pieces out of living right whales. Once again, I am not implying that these are concepts that would guide the behavior of a right whale or a gull, I mean only that during future travels, having left an area where they are attacked, right whales might linger in a new area if they found it suitable and did not experience gull attacks there.
Of course, a good place for whales to find inexperienced gulls would be tropical waters, because gulls don’t live in the tropics. (I remember being shocked to discover that gulls are absent from Hawaii, Sri Lanka, and the Seychelles and that it is crows, and to a lesser extent tropic birds, that occupy traditional gull niches in the tropics.)
The question we have yet to answer is why right whales abandon areas they may have occupied for many years, even sometimes returning to that same areas after several decades of absence. Something is causing them to leave one area to occupy another. Whatever the cause, the timing of its appearance and disappearance has a lot to say about what the cause of this behavior may be. It does not take centuries, geological ages or epochs for right whales to abandon one area and move to another; it doesn’t happen in a few weeks or months either; Times between moves seem to be years and decades.
A behavior like avoiding gulls that learn to attack them fits such a schedule. Kelp gulls have an average life span of 30 years, so any right whales that successfully reoccupy an area where the gulls once molested them would have to wait at least thirty years before returning if they were to avoid any gulls still alive that have the knowledge that it is safe to attack a right whale.
Regardless of whether feeding on right whales by South African gulls was an independent invention or was imported from Valdés, I believe the only hope right whales have for survival anywhere is for all populations that live near shores to find satisfactory, near-shore locations where the local human population welcomes their presence and doesn’t start killing them or even unintentionally creating obstacles that reduce their chances of survival.
As mentioned above, it seems reasonable to assume that when gulls start biting pieces out of surfacing whales (something that other seabirds may also learn to do someday), it eventually causes the whales to abandon that area and move to where gulls have not yet learned the behavior. It seems clear that back in 1789 something caused right whales not to be in the Península Valdés bays in the numbers they are now. 1789 was the year that Spain built a fort at the back of the same sandy beach in Península Valdés’, Golfo San José, off which one of the world’s greatest concentrations of right whales is now found. The fort was abandoned following a massacre by the local Tehuelche tribe in 1810, and was not reoccupied. The fort’s history has been well documented but there is no indication that its Spanish occupants saw whales there. Had there been a large population of right whales present as there is now, one can expect that the Spanish would probably have exploited it or at least reported its presence. The baleen of right whales was very valuable back then and Spanish Basques had been whaling from the coast of the Bay of Biscay since the 10th century—making them the earliest European whalers. But so far there is no evidence to indicate that while the fort was occupied there was any whaling for right whales, or even reports of their presence in Golfo San José. A few years later, when the American right whaling fleet moved into the South Atlantic, some of its boats found so many right whales in Golfo San José that it took that fleet five years to destroy the population.
This history demonstrates that even at peak population right whales were absent from an area they later occupied in force. It shows that something is responsible for them moving from one area to another. I believe that a likely cause is bird attacks, from which I conclude that because whale watching has become a major industry there, if right whales are eventually driven out of Península Valdés it will have a serious impact on the region’s economy.
However, that is really a secondary effect; the people of Chubut are resourceful and have recovered from other serious economic blows before. As for the whales, surely there are many kilometers of beaches elsewhere in South America that they could occupy. However, the same people who would suffer most if the whales abandon Valdés have a quality that is unique in my experience: when it comes to protecting and understanding what these whales require, and to making sure that that information is part of their children’s education, the people of Chubut are the best informed, most active population of advocates for whales that I know, anywhere in the world–and I am well calibrated in this respect.
For this reason, I conclude that it is very unlikely there are other unoccupied coasts anywhere in the western South Atlantic that the Argentine population of endangered southern right whales might occupy in which they would have as good a chance for survival as the one they currently have along the Chubut coast.
Another characteristic of an area satisfactory to Right Whales is shown by their preference for shallow water with a sandy or muddy bottom that is free of rocks. Such areas are uncommon along the South American coasts in latitudes the Right Whales prefer; there it is rocky bottoms that are most common. The same is true of the South African latitudes that are frequented by Right Whales.
In summary: I believe that the loss of right whales in the waters of Península Valdés would be a disaster not just for the people but for the whales. For all of these reasons it is my reluctant opinion that the only way to prevent an otherwise inevitable loss for both people and right whales is to reduce the population of Kelp Gulls.
I fully realize that making such a suggestion can only damage my reputation, for I have spent 50 years focused on trying to conserve many forms of ocean life—not just whales. However, the fact that I nevertheless suggest that the kelp gull population be reduced at Valdés is indicative of how serious I believe the problem is that the gulls are causing right whales.
Kelp gull populations recover quickly. Their close relative, the Northern Hemisphere, black-backed gull—a species, as I have noted, that some consider to be the same as the kelp gull—was brought to near extinction when its feathers were used to decorate hats. However, it recovered fully and the IUCN Red Book now gives Dominican gulls the status of: “Least Concern.”
Recently lots of southern right whale calves died. We don’t yet know for sure what is killing them. It appears not to be infections of the wounds the gulls make. But most calves have many. Once a gull has opened a lesion, it and other gulls repeatedly aim at the lesions, enlarging them over time so that some calves have no skin left in the region of their backs that are exposed to air when the calf surfaces to breathe as the result of hundreds, even thousands, of bites. To put it differently; they are great, open sores, many of which are the size of scatter rugs.
This means they must cause calves serious grief. Simple loss of water and other bodily fluids is one consideration. They must, at the least, be painful, particularly when brushed against by the mother—for right whale mothers frequently stroke their calves with their flippers.
Lest one get the impression that calf loss at Valdes has not been a serious problem: In the seven seasons between 2007 and 2013 a total of 563 right whales were found dead, 97 percent of which were calves. This means that anything that weakened calves in that time period is, at the very least, a cause for concern, even though we still don’t know what the principle cause for this period of high calf mortality.
It seems safe to assume that calves are weakened by the wounds the Kelp Gulls create in their backs and any stress this causes them may increase their vulnerability to a variety of other factors. There is a chance that whatever caused the massive calf die-off mentioned above has stopped, because even though the attacks by gulls have not stopped, the rate of high calf mortality has. Nevertheless, about 30 dead calves are seen each year but that is the expected loss rate for a population this size.
If the attacks are allowed to continue and the whales leave the waters around Península Valdés but after an interval of decades, a remnant population returns from some distant elsewhere, the local Chubut citizens will have lost their knowledge about these whales and of how to ensure their wellbeing. Furthermore, during the whales’ absence from Chubut structures may have gotten put in the bays that make the whales’ lives more difficult. Local peoples will also have to be re-motivated regarding what the needs of this rare species are. This will require the organization of groups that promote the welfare of right whales—a task that takes years and that can be derailed even by minor political missteps. The behavior of the current Chubut administration must be praised for having wisely responded so positively to the local Chubut citizens keen interest in the wellbeing of their whales. It is for this reason, and with emphasis on the fact that the stress caused by constant gull attacks (of the gull wounds) must weaken the whales, that I believe it is critical to reduce the gull population, and that if it is not done the whales are likely to abandon the area. The 563 right whales that died between 2007 and 2013 was, of course a minimum count of the mortalities—we could only count corpses that we were able to find. Any that were carried out of the bays by wind and tides or were whales that were killed and eaten by sharks or killer whales before they stranded on some beach would increase that mortality.
The fact that kelp gulls have now initiated the same behavior in South Africa should also, I believe, be treated as an emergency, and as soon as possible the gulls there should be reduced in number—hopefully, soon enough to prevent the spread of this behavior along the entire South African coast. Though a dire recommendation, I believe that reducing the gull population, is better than doing nothing—something that seems bound to result in a much worse future.
If the idea of culling gulls is as repugnant to you as it is to me, it may help to know about another recent behavior that South African kelp gulls have invented. It takes place in Dorob National Park, which lies along the coast of Namibia and includes a colony of several thousand Cape “fur seals,” (the sea lion, Arctocephalus pusillus). The gulls have learned to attack newborn Cape fur seal pups by pecking out and eating their eyes. Once the pup is blind the gulls attack and eat such soft tissues as the genitals, the anus and the underbelly—a ghastly trauma to which the blinded pup eventually succumbs. It is not a rare activity; over 15 years of study, scientists working in the area have seen kelp gulls attack newborn Cape fur seal pups over 500 times. About half the attacks were successful enough that the gull got to eat the pup’s eyes. Whatever else can be said about culling kelp gulls, if the population is temporarily reduced, it will at least benefit right whale calves and newborn Cape fur seal pups.