7 replies to this topic

[DIProgan]

I've used http://www.utilitari...nimals.html  to come up with a number of (2 * 10^13) vertebrate animals (individuals) in the world but now I'm looking for likely numbers for how many vertebrate animals that are born and die in for example a year.

A discussion about the impact humans have on this number (not number of species but individuals) are also welcome.

I'm building data concerning... well the future of everything I guess. Tough numbers to find with google. Thankful for help

Edited by DIProgan, 30 January 2013 - 02:47 PM.

[bob1]

The number you are after is highly dependent on the average life span and litter size for each of the individual animals - for instance a mouse can live about 2-3 years and have about 10 pups every 6-8 weeks from the age of 2 months (under optimal conditions, birth rates and litter size tend to decline with age after about 1 year), whereas something like an Orangutan or an Elephant may live for 60+ years and have only 1 birth every 3-5 years.  That's just the mammals who typically have a K strategy where most survive, but something like a turtle may lay a hundred or more eggs (when do you consider them born?) but have a R strategy, so the number that survive is few.

You could make the assumption that roughly over time established populations are more or less stable in terms of numbers.

[DIProgan]

The divider here is when an animal would feel pain because of dying so to make that part a bit easier even if it is not the absolute truth: eggs being eaten would not be considered a death but anything hatched or otherwise alive when arriving into the outside world and dying seconds later would be considered a death.

Populations are stable even with our human influence?

[bob1]

How do you measure pain? Put a nereid worm (osmo-conformer) in fresh water when it has been in salt and it will wriggle a lot, but isn't protected under (any that I know of) law as an animal that must be humanely killed.  I would say that all vertbrates and any multi-cellular animal will feel a form of pain, but how do you measure it?

Stability of populations -depends on the species a lot.  You hear about the cute furry ones such as tigers and pandas, but have you heard about Orange Roughy (fish species, massively overfished despite limits on catches, population crash etc. now quite rare, but extremely ugly) We can't even begin to measure the stability of many fish species, not even those that are commonly fished.  Mice and Rats - probably on the increase gven the spread of humans.

The answer you are looking for can't even begin to be estimated, so you have to make some assumptions.

[hobglobin]

Yes it mainly depends on species, but a general trend may be that generalist species with no special needs in terms of habitat, diet, climate etc (also called ubiquitous, euryoecious or eurytopic, considering the different factors) have stable populations or increase even (examples are rats, mice, raccoons, sparrows, pigeons etc), whereas specialist species with quite narrow niches and specialist needs concerning the mentioned factors have often declining populations (stenotopic, stenoecious species). Examples are the koala, many amphibian species, wildcats, polar bears, bats).
I think nowadays more or less all factors influencing this are influenced finally by human beings. The most important factor here is the loss of habitats and landscapes where such species can live, such as rainforest or wetlands (the discussion about this should be known, agriculture is the keyword here). Other factors are pollution (see condor), poaching (especially large animals) or climate change (displacing animals with special climate needs).
I think the best data are available for large animals, birds and also amphibians, as here public interest and therefore good research networks and money exists. But it also depends on the areas/continents. Places such as US or Europe are more or less well surveyed but others such as southern America, Africa or as an extreme example the deep sea are less or not at all investigated.
Domestic animals and cattle are a different topic, as they are out of the natural cycles and depend on human support almost only. I'd say their numbers depend on economic factors, and because today the meat consumption increases, the prices are falling, their numbers increase too (as efficient production as possible of high numbers for a low price similar to other mass-produced goods).
About fish I've not much idea but I agree that the economically used species are massively overfished. They will not die out but are finally so rare (and then stable at low level) that it's useless to try to catch them and then other species are more used. Anyway some really endangered species exist (some tuna and shark species).

[DIProgan]

bob1, on 02 February 2013 - 12:08 AM, said:

The answer you are looking for can't even begin to be estimated, so you have to make some assumptions.

And I did, the assumptions are as follows: Vertebrates that hatched or otherwise entered into the world.

hobglobin, on 02 February 2013 - 05:04 AM, said:

Yes it mainly depends on species, but a general trend may be that generalist species with no special needs in terms of habitat, diet, climate etc (also called ubiquitous, euryoecious or eurytopic, considering the different factors) have stable populations or increase even (examples are rats, mice, raccoons, sparrows, pigeons etc), whereas specialist species with quite narrow niches and specialist needs concerning the mentioned factors have often declining populations (stenotopic, stenoecious species).

Thanks for input

Edited by DIProgan, 07 February 2013 - 01:14 PM.

[bob1]

DIProgan, on 07 February 2013 - 01:10 PM, said:

bob1, on 02 February 2013 - 12:08 AM, said:

The answer you are looking for can't even begin to be estimated, so you have to make some assumptions.

And I did, the assumptions are as follows: Vertebrates that hatched or otherwise entered into the world.

But that's not an assumption - an assumption is to say that over time, these populations are probably stable (births= deaths), saying that animals being born is when they hatch or pop out of the mother is a definition of a parameter.

[DIProgan]

Free to make further assumptions on your own to help the estimation.

Edited by DIProgan, 08 February 2013 - 03:18 PM.