Evolutionary biologists at one time thought that mortality risk for wild animals was so high for that before an individual got old enough to start slowing down, reproducing less well, evading predators less well, etc., it would die of external causes. This misconception has been demolished by studies where individually recognizable markings or bands allow the tracking of individual animals through their lives. Many hundreds of studies have shown that wild animals of diverse species suffer all sorts of downsides from aging.
In an iNaturalist context, I would like to know of any observations of animals in the wild that seem (based on locomotion, skin, eyes, behavior) to be showing sign or symptoms of aging. When we encounter an animal in the wild we generally don’t know how old it is, but just like we can recognize an older human on first meeting, it seems like at least sometimes a naturalist will recognize the same in a wild animal.
I’ve searched for projects or forum topics covering this, but haven’t come up with anything. I’d appreciate hearing your thoughts on the matter. Thank you.
In my experience with rattlesnakes in the Bay Area, they tend to get darker and lose contrast in their markings as they age. Large snakes (presumably on the older side) are almost always dark and muddy looking compared with smaller, younger snakes.
I don’t think so? But I don’t see enough snakes, sadly, to really have much of a sample size, and I’ve only ever seen a few real big rattlers. And with reptiles especially, temperature can affect their responsiveness and mobility.
Thank you for raising awareness to the topic of aging and wild animals. As a gerontologist, I also appreciated your comment, “recognizing an older human upon first meeting” - which is an interesting process in some social/cultural groups in terms of how “older” is defined or recognized in society. Whether ranging from “senior” discounts or Census Bureau designation (65+) or AARP membership, the good news is how being active in the outdoors and being active in naturalist activities (e.g., observations - identifications) such as birding - can be a positive aspect of the aging experience. My own goal is to learn more of the role of Orca grandmothers in the lives of grandcalves. This would be an interesting connection between the grandmother hypothesis with aging humans as well (see: https://onlinelibrary.wiley.com/doi/full/10.1002/9781118924396.wbiea2162
Citation for published version:
Nussey, DH, Froy, H, Lemaitre, J-F, Gaillard, J-M & Austad, SN 2013, ‘Senescence in natural populations ofanimals: Widespread evidence and its implications for bio-gerontology’, Ageing Research Reviews, vol. 12,no. 1, pp. 214-225. https://doi.org/10.1016/j.arr.2012.07.004
Interesting thread. In our region for mammals, biologists also elicit age through hunter harvests, by counting tooth rings. Recently a wild black bear sow was dated to 31. Curiously, it was reported to be acting in an erratic fashion, perhaps due to senility. By this age, the bear has mostly lost its teeth except for molars. For grizzlies, they’ve also been observed to change feeding strategy:
Opinions are varied. There are so many people on earth that there must be many kinds of biologists/scientists. Recent news on very long life creatures include Greenland sharks, clams, some trees are known to live for a long time, such as some olive trees. There is a fig tree that just keep expanding horizontally and basically it can live forever. There was an article of a carp living in a cave with stream…
Not all creatures are the same. so there are exceptions within one species or across all species. One can write in a general manner.
The primate species I work with has distinctive changes in color and pelt texture at different points in its lifecycle making it easy to estimate age for younger individuals and relative age for mature individuals.
One of the challenges in something like this is that any changes, if visible at all, are likely to vary by species, or be of traits that are difficult to capture in the type of casual observations that are the most common on iNat (eg. teeth).
I know with red-eared sliders, the “red ear” fades on older individuals but don’t know at what age this occurs. The only other species I know about aging with is the Virginia Opossum. They don’t stop growing in life and will continue to grow until their body has outgrown their organs so typically, the bigger the individual the older it is.
This thread really gave me food for thoughts about aging, especially programmed aging vs “wear and tear” (thank you @hawksthree for the links!). This observation of a bumblebee immediately came to mind. I wonder whether that might make designing iNat projects around aging more difficult (ie telling injury from aging).
Delving further into this might require a slightly more relaxed headspace than where I’m at right now, but it is a fascinating topic!
This reminded me of this observation from a few years ago. While I am not certain this was an older individual the faded coloration on certain parts of its body, and the way it moved across the trail all made me feel that it was quite old.
The Giant Bumble Bee from Chile is orange, very orange, with black dark legs and wings, but when get old, they lose their hair and tend to pale orange as far I know, this is not documented oficially.
Sometimes people find shelled mollusks whose shells are gerontic in appearance. That means the shell is very thick and may be distorted somewhat in shape,
I don’t have any observations that I can show you though.
Possibly not helpful but I observed this wild Sun Bear late last year that appears to have a cataract on its left eye. Cataracts aren’t always caused by age of course, but the behavior of this bear would also suggest it is aging: It was far less cautious than this (usually extremely shy) species would usually be.
The examples @egordon88 and @graysquirrel offered of wear in insects are the ones that come to mind for me, but they are also good illustrations of a key point with aging: some species (including many of the insect examples) are essentially “annuals” that are going to die at the end of the year no matter what, while other species have an ability to survive for multiple years. We would expect aging to look quite different in these groups. In groups that only live for one year regardless, we’d expect low evolutionary pressure for maintenance of the body/prevention of visible signs of aging. Organisms should generally invest in maximal reproductive output (and just enough in survival to get there) to maximize fitness.
In organisms capable of surviving for multiple years, we should expect more investment in maintenance of the body (and potentially fewer signs of aging) as access to reproduction in additional years can increase fitness. It’s also often to an organisms advantage to hide outwards signs of aging or senescence. These signs could be used by predators to target organisms that are slow/weak/less energetic in cases of high age, so we might expect adaptations to conceal or mitigate these signs, just as organisms conceal the effects of injury. However in organisms that only live one year (as above) there might be less investment in reducing signs of aging, so they might be easier to spot.