Animal metabolism thread.

[Supercommunist]

Been researching this topic, figured I'd share the info:

DEI = daily energy intake.



Source:

journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0050022

After accounting only for body mass effects, variation of more than 20 times between lowest and highest still exists. A simple way to demonstrate this is to calculate predicted FMRs for a 100-g mammal, bird, and reptile using the equations in Table 2. The results are 142 kJ/day for a 100-g mammal, 242 kJ/day for a 100-g bird, and 11.8 kJ/day for a 100-g reptile (see Table 2). The bird has to use 20 times more energy to live each day than does the lizard, and the mammal pays 12 times more than the lizard. Thus, there are large differences between these three taxonomic classes of animals.

Source:

ENERGETICS OF FREE-RANGING MAMMALS, REPTILES, AND BIRDS

An estuarine crocodile requires approximately 4% of their body weight every week to maintain its body mass [6]. As such, a large crocodile of 1,000 kg would need 40 kg of food per week. Feral pigs weigh between 50–100 kg; thus, many crocodiles could take advantage of this prey that is large, abundant, and relatively easy to catch to satisfy their dietary requirements.

I feel this might be a bit of a high estimate though because this estimate was based off a young crocodile's needed energy intake and thus might not be appropriate to just scale up:

journals.plos.org/plosone/article?id=10.1371/journal.pone.0197159

[Infinity Blade]

I feel this might be a bit of a high estimate though because this estimate was based off a young crocodile's needed energy intake and thus might not be appropriate to just scale up:

Yeah, the larger an animal gets, the less food it needs to eat relative to its body mass (but the more food it needs to eat in absolute terms).

[creature386]

Yep. Good ol' Kleiber's law (and animal's metabolic rate only scales to the 3/4th power of its mass).

Since this is the right thread to ask this question: Is it true that ectothermy can limit body size? Because an argument I've heard in favor of dinosaur endothermy is that ectotherms supposedly rarely get heavier than 1 t (though, I suppose some extinct crocodiles would like to say Hi). The argument is mostly that ectothermy limits the muscle power a large terrestrial animal would need. I've seen an interesting graph on that in one of my lectures, but I'm most certainly not allowed to share it here and I can't find it online anywhere.

[Supercommunist]

Megalania was also a lot larger than many endothermic predators so I am not sure I buy that argument.

A lot of research I have been looking at seems to suggest that humans have pretty slow metabolisms compared to a lot of other mammals.

Apparently 30 kg dogs need about as much kcals as a human.



pubmed.ncbi.nlm.nih.gov/25313818/

[Supercommunist]

According to a study I found: neanderthals needed 4,070 k calories while Pleistocene humans required 3,788.5 k calories per day which is a lot higher than the average 2400 kcal requirement today.

www.nature.com/articles/srep44707/tables/6

[Infinity Blade]

I guess since they were much more active than the average person today they would have needed significantly more calories.

[Supercommunist]

According to one study, a 660 kg rex would only need as many calories as human. This sounds like a huge underestimate to me though as other studies I read claims a 160 kg male requires 6300 kcal's a day and female polar bears require 12k kilocals a day.

This was done to ensure we would not produce an exaggeration of the differences between taxa as, for example, the estimated dally caloric intake according to BMR using [55] for the 660 kg juvenile tyrannosaurid “Jane” is only 2400 calories or about the same as the lead author.

journals.plos.org/plosone/article?id=10.1371/journal.pone.0223698#pone-0223698-t003

As a result, the FMR of polar bears is high relative to predictions for terrestrial mammals generally (25) and consistent with expected levels derived solely from other mammalian carnivores (26). Our measured FMRs averaged 1.6 times previously assumed values for polar bears (SE = 0.1, range = 1.0 to 2.6) (13, 14). Daily FMRs measured over 8 to 11 days, averaged 0.45 ml CO2 g−1 h−1 (SE = 0.04, n = 9 bears), which converts to 51.6 MJ day−1 (SE = 6.2, n = 9 bears) or 12,324.7 kcal day−1.

www.science.org/doi/10.1126/science.aan8677

[Supercommunist]

Some papers have estimated that a 8 ton Purussaurus would have required 22 to 60 kg of meat a day.

This work estimated that the Purussaurus brasiliensis specimen was 12.5 m long in life, weighed 8,424 kg (around 8.4 metric tons), had a daily food intake between 21.6 kg and 59.5 kg, and was capable of generating a sustained bite-force of 69,039.2 N (around 7 tons-force).

journals.plos.org/plosone/article?id=10.1371/journal.pone.0117944

Generally speaking exothermic reptiles required 10 percent of the food and water a similar sized endothermic mammal would need. Birds tend to have higher metabolisms but an ostrich metabolism is comparable to a similar sized deers so I think theropods likely had mammal-like metabolisms as well.

So I suppose there is a decent chance that megatheropods would have needed 200 to 600 kg of meat a day.

[Supercommunist]

Total FMRs varied by age and sex, which is partly due to the long developmental period and sexual dimorphism in killer whales. FMRs for males (465–4,434 kg) ranged from 35,048 to 228,216 kcal/d while FMRs for females (465–3,338 kg) ranged from 35,048 to 184,444 kcal/d. DPERs were calculated from FMRs assuming a standard digestive efficiency. Corresponding DPERs ranged from 41,376 to 269,458 kcal/d and 41,376 to 217,775 kcal/d, respectively.

A 4,434 kg orca requires 269,458 kilo cals a day.

d1wqtxts1xzle7.cloudfront.net/40367896/Basal_metabolism_of_an_adult_male_killer20151125-27190-i034ly-libre.pdf?1448467765=&response-content-disposition=inline%3B+filename%3DBasal_metabolism_of_an_adult_male_killer.pdf&Expires=1720898140&Signature=baivyjbuDo3H2qKkgKoqHwX6bsg4p5kqAlMukMEVcTU74UnmzUuPdcD1XxOVKozv2inJeiCRAyyD0TEs2y4HWraYd5HQBgoQAgT4Q8datYqKlWTYu5XXKyW4xANoXiragxF5ZT5IaMJuRwFcs67FO6QY8GFFq30HBI6r~CQriO0VArmozEOab55Jhm6WbYk8AnaXM6CB74v6GoiW5Jm~J~~9-gslJDZQjxjPonBzAi-t-pWm1HOfF7aJ~GJ3M9UtqDRuumzo2AF4Z59bX2Hp-Xf62HPEylAPczZwXlRlbfXjSH-2t9DzT3pzNCb6ZNbuwZM-KJ5Scxdw0OAaF78VnA__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA

According to a cook google search, a pound of beef provides 1,137 kilocalories (chicken and pork are about a 100 calories lighter) I don't know whether it is more energy intensive for multi ton animals swim or walk, but it sounds like based on that a similar sized theropod would need about a 150 pounds of meat a day if there metabolic and energy requirements were similar.

Then again, orcas are really intelligent so it is possible that they burn more calories than other similar sized animals.