My opinion is that under-nutrition might lead to predator success and injury and so on . Death is normally multifactorial so it is not case of one versus another. But you would expect a nutritionist to say that food is important!

Hello

It's impossible to answer this for an overall-kingdom-animalia perspective because of the biodiversity but mostly die of disease or wounds, starvation, predation, or their habitat is destroyed . but it's not exactly the same for all animals . Also , the cancer can kill wild animals at similar rates for human .

Interesting question Lewis. It does have a feel of one of those existentialist questions that can never be properly answered, and I agree with both previous that "death" often has multifactorial causes from location to location and year to year, let alone species to species. If, however, you're looking for a sort of contributory causes line of investigation, there have been a few good examples undertaken in Australia. Specifically, I can think of Quokkas on Rottnest Island, which were extensively studied by Don Bradshaw, among others, and Tammar wallabies on Garden Island, studied by Brian Chambers. I'd also go looking into Hamish Campbell's work on Cassowaries, and I think Don Bradshaw also did some good work on fauna deaths on Barrow Island back int he 1970's, but I can't guarantee it. Then of course there's the plethora of studies on male semelparity in dasyurids, but I guess nobody knows the proximal cause of death. There's lots of ideas that it might be loss of body condition, immune problems and disease, predation due to being to "shagged out" to run away. I guess this raises the question of proximal vs ultimate cause.

Essentially, Quokka's on Rottnest die from disease and loss of condition, which is precipitated over the summer by a lack of water sources on the island. Tammar wallabies, from memory, die principally from road accident, but outside road transit areas maintain pretty good health and body condition throughout a year (predators other than cars are absent from this system). I can't exactly recall the story with Cassowaries, but road deaths rate pretty highly.

For an example with small mammals, check out "Patterns of Mortality in a Wild Population of White-footed Mice" (Collins & Kays 2014) in Northeastern Naturalist. I believe Collins has published more extensively on the subject as well.

Generally, i think that the living organisms die as they loss the ability to repair the errors occurring in their cells or loss the ability to renew the ruined cells .

                                         {No repairing , Death is soon}

Dear Lewis

Survival ability did its job within natural selection process, all organisms reproduce and give offspring exceed the environment support, so all will struggle to continue in the life and contribute in offspring of the next generation ( the fitness of individual ) , individual with low fitness will leave ( die no matter about reason ) because its genotype not fit and not support  the needs for the changes in environment .

Good Luck

This is a very broad topic. Do you take in to account for animals that are completely in a natural environment, or wild animals that are in areas changed by humans?

I agree this is an extremely broad topic with any even broader realm of answers.  Infectious diseases, such as bacterial infection, pnuemoniae, septicemia from a wound, viral, etc. are real causes.  In past experiences doing necropsies on wild animals I routinely observed infections including severe parasitic infections which can invade the GIT, lungs, kidneys, liver (this is why I do not advocate feeding domesticated animals raw diets, the argument by supporters may be that their ancestors ate raw meat, but wild animals have a much shorter lifespan and a high incidence of parasitic infections!).  Also, wild animals don't receive vaccinations, and can contract and die from tetanus among other things.  They may get shot by a hunter or poacher, hit by a car, eaten by a predator, a nutritional deficiency, toxemia, or get naturally occurring disease processes that any living being is susceptible to, such as cancer, etc., assuming they are able to survive through the other mentioned threats first

This is a broad topic indeed because there is much temporal and spatial variation, and details such as the size of the animal may be important - anyone can kill a small animal but not an elephant. Visual observations or individuals found dead do not reveal the complete story because most individuals just disappear. Studies utilizing radio transmitters have revealed that most small mammals or birds living in natural or semi-natural conditions are killed by a predator. If predator populations are kept low or the predators do not find the site for some reason, starvation and/or diseases take the dominant role. In the latter case, population dynamics often follow a boom-and-bust pattern with sharp crashes. Some radio-tracked animals have died in accidents, typically

Well this topic has attracted a huge range of comments, and I find it particularly interesting to consider what people think of as "causal". I return to the duality here of proximal vs ultimate causes of death. There's a lot of comment here discussing parasites, diseases and other immune compromises (cancer being in this category to my mind). From the perspective of the organism, these are the proximal cause of death, but surely not the ultimate cause in most cases? Most animals have an immune system that can deal with these kinds of assaults unless the immune system itself is stressed by an over-arching ecological cause. My own bias leads me to think about energetic stress, water stress, or some other cause of chronic stimulus (like the semelparity examples).

Similarly, predation and misadventure turn up a lot in telemetry studies as causes of death (at least in my limited experience with fauna of conservation significance in Australia). With a proximal cause like this it's even more difficult to unpick an ultimate cause. Was the victim weakened in such a way as be unable to avoid the predator? Was it a species of predator against which the victim had no evolved defences (Australia is good for examples like this)? Was the predator a particularly fit example of its species? Is this all just down to chance?

As previously stated by all, a really broad question, but I think before you get at questions like the one raised by Emmy Leung you need to understand how proximal and ultimate causes interact. How can you ask whether anthropogenic disturbance has increased animal deaths if you don't understand how anthropogenic disturbance can influence causes of death? Road trauma is pretty easy to understand, but the increased hunting efficiency of predators in fragmented landscapes resulting from increased movement capacity along roads is a pretty convoluted thing to unravel. I'm not sure that I've ever seen that quantitatively linked to increased deaths in animal populations, but that is one of the environmental management positions that we work from here in Australia.

Thank you very much for all your erudite responses to my question - this has been super helpful. Much obliged, Lewis

i once read a lot about natural deaths in animal populations. there are a few excellent studies. like those (sorry, cancer and whales)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1502934/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1240769/

https://www.ncbi.nlm.nih.gov/pubmed/27068500

they deal mainly with cancer, but give answers beyond it. whales are ideal for autopies as they get collected after death on beaches and one can find them. but there are also paper on domestic animals. e.g. dogs:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1476436/

heart and toxicity followed by GI and trauma. and in cats:

https://www.ncbi.nlm.nih.gov/pubmed/11195527

trauma and heart... ok. there is also baboons and early life events:

https://www.ncbi.nlm.nih.gov/pubmed/27091302

oh. and looking in zoos would be a good idea maybe:

https://www.ncbi.nlm.nih.gov/pubmed/27862242

Hi Oliver, many thanks indeed for all these great links. I'll definitely be taking a good look through them. I hadn't thought of autopsies and zoos etc.

Thank you again to everyone who responded to my question. These responses were fundamental to helping me write a 'popular piece' for the magazine of the Royal Society of Biology - 'Biologist'. I have uploaded a pdf of the article to my RG page if you would like to take a look.