I’ve always found friendly interactions between animals of different species to be oddly reassuring. After all, the world can’t be all that bad a place if two animals, separated by differing genetic backgrounds and behavioral imperatives, can find a way to reach across the biological divide and share something, something joyful and positive.
Because of this, I’m an absolute sucker for all of those YouTube videos of cats curling up with mice, horses who befriend sheep, elephants and dogs who are inseparable, and the like. You know the ones I mean.
Many times, though, these are artificial pairings that spring up after we humans have altered the environment, habituating or even confining the animals with one another. While these human-influenced relationships can be incredibly heartwarming, it somehow seems even more magical when animals forge connections across species boundaries in the wild, in their native habitats and without any human intervention.
With that background, I’d like to introduce a paper published last year in the journal Aquatic Mammals1, which reports on two separate playful and – as you’ll see – uplifting encounters between bottlenose dolphins (Tursiops truncatus) and humpback whales (Megaptera novaeangliae).
The first took place on a January afternoon off the northwest coast of Kauai, when a group of eight bottlenose dolphins met up with a pair of humpback whales. Two of the dolphins – apparently adults – approached one of the whales, first appearing to surf the pressure wave created by the whale’s head as it swam, and later taking turns lying perpendicularly across the whale’s rostrum when it surfaced to breathe. Then, while one of the dolphins lay balanced over the end of its rostrum, the whale stopped and slowly lifted the dolphin high into the air. The dolphin maintained an arched position and made no effort to escape, allowing the whale to continue lifting until it was nearly vertical in the water, at which point the dolphin slid down the whale’s rostrum, dove into the water, and porpoised back to its fellow dolphins.
Here’s a color photo of the dolphin just about to go whale-sliding:
Look Ma, No Hands! (photo credit: L. Mazzuca)
And here’s a black and white series of shots that captures the full adventure sequence:
The second encounter also occurred on a January afternoon, this time off the northwest coast of Maui, when an adult female bottlenose dolphin swam up to a mother humpback whale and her calf. After diving underwater, the dolphin and mother whale resurfaced with the dolphin resting across the mother whale’s rostrum. The mother then proceeded to lift the dolphin a total of six times over 8.5 minutes, with the dolphin either lying on her stomach or right side during the lifts, which varied in length from four to 45 seconds. Again, the dolphin made no attempt to escape and held her position in such a way as to facilitate the whale’s lifting.
Here’s a sequence of photos showing this second duo demonstrating the proper technique for lifting a relaxed-looking dolphin:
The authors of the Aquatic Mammals paper considered alternate explanations for these interactions, including whether they represented an aggressive whale response to an antagonistic dolphin approach, whether the whales were demonstrating concern regarding perceived distress in the dolphins, or whether the cetaceans were simply playing together. They found the first two hypotheses to be unlikely – among other things, the interactions were too cooperative and relaxed in pace to be aggressive, and the dolphins were in good health and showed no evidence of distress. In the end, while the authors didn’t rule out the possibility that maternal instinct was involved in the whales’ lifting behavior, they concluded that the best explanation was that these were simply instances of interspecies play between the bottlenose dolphins and humpback whales.
Further, these bouts of play between dolphins and whales may not be all that uncommon, as back within the friendly confines of YouTube I was able to locate a video documenting another episode in which a bottlenose dolphin went for a ride on the rostrum of a humpback whale:
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Play may serve a number of important purposes – for example, it may provide an avenue for intelligent, social animals like dolphins and whales to experiment with their surroundings, hone their physical skills and learn how to interact collaboratively with others. But aside from any practical evolutionary significance, I like to think of these encounters as illustrating how animals can, on occasion, take a few minutes away from the serious business of survival to share some pure joy and wonder with a fellow being, even a fellow being of a different species.
So, all of this is comforting. If dolphins and whales (and other animals who form interspecies bonds) can find a way to communicate playfulness with each other and to share experiences without any kind of a common language, perhaps we humans can do a bit better ourselves. Maybe some of the divides we see today – political discord, religious conflict, international posturing, cultural and racial inequities – aren’t so unbridgeable after all. Perhaps all we need to do is to remember an uplifting dolphin story or two.
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1Deakos, M., Branstetter, B., Mazzuca, L., Fertl, D., & Mobley, J. (2010). Two Unusual Interactions Between a Bottlenose Dolphin (Tursiops truncatus) and a Humpback Whale (Megaptera novaeangliae) in Hawaiian Waters Aquatic Mammals, 36 (2), 121-128 DOI: 10.1578/AM.36.2.2010.121.
I’ve been thinking about grief lately. It can be so overpowering – the dull ache of emptiness, the stabbing pain of loss, and the prism of sadness that transforms the bright colors of everyday life into a harsh and alien landscape. Consumed by grief, we are alone; yet somehow our solitary suffering can end up strengthening the bonds we have with others we know and love.
I’ve also been thinking about grief in animals, and what we know about it. When our cat Puggsley died, our younger Siamese, Moose, felt the full impact of the loss. The two had always been close, perhaps tied together by their mutual skepticism over Wednesday, our third cat and official people-pleaser. Moose and Puggsley were constant companions, playmates, napping buddies, and a rather frightening pair of mischief makers. When Puggsley became old and frail, he would curl up stiffly by the fireplace, and Moose would bed down near him. At the very end, Moose was right there, tenderly licking Puggsley as he was overcome by a seizure. And after he was gone, she mourned – she was lost without her friend, and had little appetite or energy for weeks. She never bedded down by the fireplace again. How do I know this was grief? Well, it was obvious; I just know.
Puggsley and Moose
But what do we really know about grief in animals – that is, in a scientific sense? Not particularly much, it turns out.
We are (mostly) beyond the era in which animals were considered thoughtless automatons, incapable of feeling pain and other emotions. Still, there have been relatively few formal studies of how animals experience grief.
In a way, this isn’t so surprising. For one, opportunities to systematically observe grieving behavior in the wild are rare and, if you think about it, it’s difficult to design ethical studies intended to cause social animals to grieve in captive settings. Also, what specifically do you test for and how do you quantify and evaluate an inherently subjective experience like grief? It’s tough enough to evaluate this sort of thing in humans, who can respond to questionnaires and use language to express their emotions….
As a result, most the scientific literature about grief in animals is anecdotal or observational in nature, and in many of these accounts it’s clear that otherwise objective researchers have struggled to come up with scientific ways of reporting what, in the end, are their own reactions, what they just know.
Although the record is sparse everywhere, there have been some recent papers on grief in primates. Brian Switek, who writes the Laelaps blog for Wired Magazine, has written a terrific piece on this research in his “What Death Means to Primates” posting (I strongly encourage you to check out Laelaps; it’s one of the best blogs out there on paleontology, evolution, and the history of science).
As Brian recounts in detail, studies have documented chimpanzee and other primate mothers who have continued to carry dead infants, sometimes for weeks and even to the point of mummification. In one of the studies1, researchers described two chimpanzee mothers (Jire and Vuavua) in Bossou, Guinea, who carried their dead babies (aged 1.2 years old and 2.6 years old, respectively) after they had died in a respiratory epidemic, grooming them regularly, chasing away flies, and carrying them during all travel. The researchers pondered:
An obvious and fascinating question concerns the extent to which Jire and Vuavua “understood” that their offspring were dead. In many ways they treated the corpses as live infants, particularly in the initial phase following death. Nevertheless they may well have been aware that the bodies were inanimate, consequently adopting carrying techniques never normally employed with healthy young (although mothers of handicapped young have also been known to respond appropriately).
In another study2, James Anderson, Alasdair Gillies and Louise Lock reported on the peaceful death of an older chimpanzee, Pansy, who lived in a safari park. They videotaped the reactions of Pansy’s companions and observed a number of behaviors that they found to be comparable to human bereavement. The degree to which the researchers sought out human counterparts to the chimps’ behavior is evident from the following description in their paper:
During Pansy’s final days the others were quiet and attentive to her, and they altered their nesting arrangements (respect, care, anticipatory grief). When Pansy died they appeared to test for signs of life by closely inspecting her mouth and manipulating her limbs (test for pulse or breath). Shortly afterwards, the adult male attacked the dead female, possibly attempting to rouse her (attempted resuscitation); attacks may also have expressed anger or frustration (denial, feelings of anger towards the deceased). The adult daughter remained near the mother’s corpse throughout the night (night-time vigil), while Blossom groomed Chippy for an extraordinary amount of time (consolation, social support). All three chimpanzees changed posture frequently during the night (disturbed sleep). They removed straw from Pansy’s body the next morning (cleaning the body). For weeks post-death, the survivors remained lethargic and quiet, and they ate less than normal (grief, mourning). They avoided sleeping on the deathbed platform for several days (leaving objects or places associated with the deceased untouched).
With this focus, it’s not surprising that they concluded by proposing that “chimpanzees’ awareness of death has been underestimated.”
Also, more anecdotally, many were moved by the apparent grief captured in this poignant National Geographic photo of chimpanzees at a rehabilitation center peering at the lifeless body of Dorothy, their long-time companion, being taken to her burial:
There has also been some research into the behavior of elephants towards the dead and dying. In one study3, Iain Douglas-Hamilton, Shivani Bhalla, George Wittemyer and Fritz Vollrath reported on the death of Eleanor, a matriarch elephant in the Samburu National Reserve in Kenya. They were able to use GPS technology to track the movements of elephants in Eleanor’s family and in other families as they reacted to her collapse and subsequent death. The researchers found that Eleanor was visited frequently by both related and unrelated elephants, concluding:
Combined with earlier work and the data of other scientists it leads to the conclusion that elephants have a generalized response to suffering and death of conspecifics and that this is not restricted to kin. It is an example of how elephants and humans may share emotions, such as compassion, and have an awareness and interest about death.
Grace visiting Eleanor's body (photo: Douglas-Hamilton, et al)
In another paper4, Karen McComb, Lucy Baker and Cynthia Moss described experiments in which they assessed elephants’ strong interest in and sometimes dramatic reactions to elephant bones and tusks. After systematically presenting elephants in Amboseli National Park in Kenya with different combinations of elephant and other animal skulls, ivory and pieces of wood, the researchers found that the elephants were significantly more interested in elephant skulls and tusks than they were in the skulls of other animals or in the wood, but that they did not demonstrate a special affinity to the skulls or ivory of deceased relatives. The following video provides a nice glimpse into the way in which elephants seem to be fascinated by elephant bones and tusks:
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Several reports have also documented cetaceans reacting with apparent grief. In one report5, for example, Mark Simmonds described an incident in which two male orcas appeared to grieve over the death of a female orca thought to be their mother. For years, the two males had spent all their time swimming with this female. After her death, the males were seen swimming together but apart from all other orcas for a day or two, repeatedly visiting the places that their mother had passed in her last few days. In another instance, Robin Baird of the Cascadia Research Collective reported seeing two orcas, a mother and adult son, swimming with a dead calf in the Puget Sound, with the mother balancing the calf on her rostrum or carrying it on top of her head and occasionally lifting it out of the water, and both adults diving deep to recover the baby when it began sinking.
Dolphin and calf (Tethys Research)
Scientists at the Tethys Research Institute related a similar occurrence off the coast of Greece, where a mother bottlenose dolphin was seen interacting with a dead newborn calf. Their description vividly underscores the difficulties in evaluating these sorts of situations from a scientific perspective:
Whilst researchers must avoid being driven by their own feelings and make arbitrary interpretations, in this case it was quite clear that the mother was mourning. She seemed to be unable to accept the death, and was behaving as if there was any hope of rescuing her calf. She lifted the little corpse above the surface, in an apparent late attempt to let the calf breath. She also pushed the calf underwater, perhaps hoping that the baby could dive again. These behaviours were repeated over and over again, and sometimes frantically, during two days of observation.
The mother did never separate from her calf. From the boat, researchers and volunteers could hear heartbreaking cries while she touched her offspring with the rostrum and pectoral fins. Witnessing such desperate behaviour was a shocking experience for those on board the research boat.
Finally, Marc Bekoff (he of the Yellow Snow fame) has written an eloquent article that includes many additional anecdotes regarding animal grief in his Psychology Today column.
Ultimately, there is much we will never be able to understand regarding how animals experience the world. We can trace commonalities between human and other animal brain structures and neural pathways associated with emotional experiences, and we can try to add more systematic observations to our collection of behavioral anecdotes, but in some fundamental ways the animal mind (and, for that matter, the mind of other humans) will always be cloaked in private experience, inaccessible to us. Moreover, as some of the accounts in this post have illustrated, our attempts at understanding animal emotions are inevitably colored by our own human experiences. We can know human grief, but how can we understand what it means to experience chimp grief, or elephant grief, or orca grief?
Nevertheless, just because we cannot fully comprehend what we see in other animals, that does not mean that grief in animals does not exist or that animals cannot lead rich emotional lives. Indeed, what we do see is a pattern that makes it increasing clear that death can impact other animals profoundly.
How do I know this? Just ask Moose, Puggsley or Wednesday – I just know.
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1Biro, D., Humle, T., Koops, K., Sousa, C., Hayashi, M., & Matsuzawa, T. (2010). Chimpanzee mothers at Bossou, Guinea carry the mummified remains of their dead infants Current Biology, 20 (8) DOI: 10.1016/j.cub.2010.02.031.
2Anderson, J., Gillies, A., & Lock, L. (2010). Pan thanatology Current Biology, 20 (8) DOI: 10.1016/j.cub.2010.02.010.
3Douglas-Hamilton, I., Bhalla, S., Wittemyer, G., & Vollrath, F. (2006). Behavioural reactions of elephants towards a dying and deceased matriarch Applied Animal Behaviour Science, 100 (1-2), 87-102 DOI: 10.1016/j.applanim.2006.04.014.
4McComb, K., Baker, L., & Moss, C. (2006). African elephants show high levels of interest in the skulls and ivory of their own species Biology Letters, 2 (1), 26-28 DOI: 10.1098/rsbl.2005.0400.
5Simmonds, M. (2006). Into the brains of whales Applied Animal Behaviour Science, 100 (1-2), 103-116 DOI: 10.1016/j.applanim.2006.04.015.
As single income families become rarer and aging baby boomers begin to play a greater role in caring for their grandchildren, people have increasingly come to appreciate how much help a doting grandmother can provide. In fact, interest in the helpful role played by the elderly has given rise to the so-called grandmother hypothesis, which posits that women have evolved to live well past their reproductive years because, free from the costs of childbearing, they are able to invest more time into benefiting their grandchildren and other younger family members, raising the odds that their genes will be carried on to future generations.1 While the strength of the evidence for the grandmother hypothesis is still being debated2, it’s certainly got some intuitive appeal (especially, perhaps, to harried young parents).
What’s also quite fascinating is that the long post-reproductive life of human females – up to a third of a woman’s lifespan or more – is extremely rare: menopause appears to be unique to humans and (somewhat controversially) certain other great apes, as well as to certain toothed whales, including short-finned pilot whales and killer whales. (It’s possible that other species of cetacean may undergo menopause, but this hasn’t been established yet; also, more to come about elderly elephant matriarchs in a later post…)
So, why is post-reproductive life is so rare? If the grandmother hypothesis applies to great apes and toothed whales, why isn’t it at work with other long-lived animals who live in socially-cooperative societies? Also, if evolution favors post-reproductive life because it provides distinct social advantages, why did menopause evolve in humans and toothed whales, given the very different social structures of humans and whales?
A fascinating study published last year in Proceedings of the Royal Society B3 by Rufus Johnstone of the University of Cambridge and Michael Cant of the University of Exeter may offer plausible answers to these questions.
In a nutshell, they found that, although humans, pilot whales and killer whales have quite different social systems, in each case older females become, on average, more genetically related to those with whom they associate. By contrast, in most other long-lived complex mammal societies, older females become increasingly less related to those in their local groups as they age.
Did grandma pinch you on the cheek too? (photo credit: NOAA)
The researchers began by developing a mathematical model that would allow them to draw general conclusions about age-related changes in the genetic relatedness of long-lived social animals as individual group members disperse, die and are replaced over time. (For those interested in such things, they based their approach on the “infinite island” model that is commonly used in considering the process of gene flow among a set of subpopulations.)
With their model in hand, the researchers analyzed three relevant social scenarios:
Males Move On. In the large majority of social animal societies, males tend to move on as they mature, ultimately mating with unrelated females they find within new social groups. In this type of society, the researchers’ model determined that, over time, an older female will become less related to her group mates as she ages. She starts out in a highly related group that includes her father, but over time her older male relatives die, and her sons, and the sons of her relatives, leave the group and are replaced by unrelated males from other groups. Her average genetic relationship to the females in the group doesn’t change much, but since her relatedness to local males declines, overall her genetic connection to the group lessens as she gets older.
Females Move On. Conversely, evidence suggests that during the course of human evolution, women were the ones that were more likely to move on to start families in new environments. (In support of this proposition, Johnstone and Cant cite the behavior of other great apes, human DNA variation patterns, and social patterns among human forager societies, evidence they concede is “far from conclusive.”) In this type of society, where males stay at home and females disperse, an older female tends to become more related to her fellow group members over time. She begins her reproductive life in new surroundings where she has few genetic ties to those around her, but as she produces sons who are likely to remain in the group, her relatedness to local males builds up over time. Again, because the degree of her relatedness to other females stays fairly constant – she starts out with little relation to the females in her new group and this doesn’t change much as her daughters leave and are replaced by new unrelated females – her overall genetic connection to the group increases as she ages.
Males and Females Stay Put, But Mating Occurs Between Different Groups. In the resident killer whale and pilot whale societies studied, males and females stay with their natal groups for life, but mating occurs non-locally, that is, between females and males from other groups. In this final scenario, even though the social structure is quite different from “female moves on” societies, the results are the same: an older female tends to become more related to her fellow group members over time. A female begins her reproductive life separate from her father and her paternal relatives (who belong to a different group), but as she has male offspring her relatedness to males within her group grows over time. Once again, her relatedness to other females stays more or less constant, meaning that her overall genetic affinity with her group increases as she grows old.
Thus for human and certain whale societies, in contrast to most other social animal groupings, a female’s relatedness to her group increases as she becomes older.
Johnstone and Natal next considered the fitness costs of reproduction. They noted that having children imposes costs on other breeders within one’s group due to increased competition for food, resources and mating opportunities, whereas cessation of reproduction confers a benefit, due to a corresponding reduction in competition. Then, using a using a statistical model involving an “inclusive fitness” approach to generate quantitative results for the three scenarios described above, they reached a not-surprising conclusion: in scenario 1 (males move on), it is less advantageous for older females to “help” younger generations by stopping their own breeding, whereas in scenarios 2 and 3 (the human and toothed whale scenarios), non-breeding “help” is favored by evolution, as it confers advantages on a younger generation that is progressively more related to the older helper.
So there you have it. Does Johnstone and Natal’s analysis sound plausible? It certainly offers a neat way of finding an underlying similarity in great ape and whale societies that may explain menopause and support the grandmother hypothesis in these very distinct groups.
No wonder cetaceans often look like they’re grinning – they’ve been spoiled by their grandmothers!
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1See, e.g., Lahdenperä, M., Lummaa, V., Helle, S., Tremblay, M., & Russell, A. (2004). Fitness benefits of prolonged post-reproductive lifespan in women Nature, 428 (6979), 178-181 DOI: 10.1038/nature02367; Shanley, D., Sear, R., Mace, R., & Kirkwood, T. (2007). Testing evolutionary theories of menopause Proceedings of the Royal Society B: Biological Sciences, 274 (1628), 2943-2949 DOI: 10.1098/rspb.2007.1028.
2See, e.g., Kachel, A., Premo, L., & Hublin, J. (2010). Grandmothering and natural selection Proceedings of the Royal Society B: Biological Sciences, 278 (1704), 384-391 DOI: 10.1098/rspb.2010.1247.
3Johnstone, R., & Cant, M. (2010). The evolution of menopause in cetaceans and humans: the role of demography Proceedings of the Royal Society B: Biological Sciences, 277 (1701), 3765-3771 DOI: 10.1098/rspb.2010.0988.
1Deakos, M., Branstetter, B., Mazzuca, L., Fertl, D., & Mobley, J. (2010). Two Unusual Interactions Between a Bottlenose Dolphin (Tursiops truncatus) and a Humpback Whale (Megaptera novaeangliae) in Hawaiian Waters Aquatic Mammals, 36 (2), 121-128 DOI: 10.1578/AM.36.2.2010.121.
paulfnorris
AnimalWise 