Comparison of feral cat with 'native cat' in Australia: differences in pace of life between Felis catus and Dasyurus maculatus

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Also see https://www.inaturalist.org/posts/67213-an-adaptive-interpretation-of-the-striping-in-the-numbat-myrmecobius-fasciatus#

One of the most remarkable differences between Australia and other continents is the lack of indigenous Carnivora - particularly felids (https://en.wikipedia.org/wiki/Felidae) - on the island continent (https://en.wikipedia.org/wiki/Fauna_of_Australia).

British settlers, nonplussed by this lack, applied the term 'native cat' (https://www.britannica.com/animal/native-cat) to the marsupial closest in appearance and habits to felids, namely Dasyurus maculatus maculatus (https://www.inaturalist.org/taxa/40166-Dasyurus-maculatus and https://www.australiangeographic.com.au/topics/wildlife/2020/08/when-a-spotted-tailed-quoll-wanders-into-your-house/ and https://www.youtube.com/watch?v=BjTyvXu-N9w and https://www.facebook.com/watch/?v=540233413267955).

So, some naturalists may assume that D. m. maculatus is a fair ecological counterpart for cats, the differences being relatively superficial results of the deep phylogenetic division between marsupials (https://en.wikipedia.org/wiki/Marsupial) and placental mammals (https://en.wikipedia.org/wiki/Placentalia).

However, the functional differences are actually profound, when evaluated in terms of energetics (https://en.wikipedia.org/wiki/Bioenergetics#:~:text=10%20External%20links-,Overview,and%20transductions%20in%20living%20organisms.).

Felis catus (https://www.inaturalist.org/observations?place_id=6744&taxon_id=118552), introduced by humans to Australia, has rapidly invaded the continent (https://invasives.org.au/our-work/feral-animals/cats-in-australia/ and https://www.dcceew.gov.au/environment/invasive-species/feral-animals-australia/feral-cats).

It has nearly usurped the niche of D. m. maculatus, leaving the latter threatened with extinction (https://www.youtube.com/watch?v=DLvPBFMn_BY and https://atlasoflife.org.au/creaturefeatures/2018/5/18/spotted-tailed-quolls and https://wildlife.org.au/hunt-for-endangered-spotted-tailed-quoll-in-logan/).

METHODS

In this Post, I have chosen a few basic parameters, to quantify the idea that, in the 'fire of life', the feral cat 'burns bright', whereas the indigenous carnivorous marsupial 'burns dull'.

This is of ecological and biogeographic interest, because it

• shows the ecological nature of Australia, and
• in less abstract terms, helps to explain the superior competitiveness of the introduced species.

It is true that placentals and marsupials differ in many ways, particularly reproductively.

However, these details can distract us from the overall differences in pace of life. For example, the short gestation of D. m. maculatus would be misleading, unless framed within the context of the overall time taken from conception to sexual maturity - which is the important parameter for the rate of reproduction in a demographic sense.

BODY SIZES

It is an astonishing - and underappreciated - fact that, at the time of European arrival, the largest, fully indigenous carnivorous mammal on the whole mainland of Australia weighed only 1.8 kg in adult females.

And even this value applies only to the larger-bodied of two subspecies, the other (Dasyurus maculatus gracilis of tropical northeastern Queensland) weighing only 1.7 kg (see Table 2 on page 140 of https://www.researchgate.net/profile/Al-Glen/publication/248902342_Population_attributes_of_the_spotted-tailed_quoll_Dasyurus_maculatus_in_north-eastern_New_South_Wales/links/542dd71b0cf29bbc126e3dce/Population-attributes-of-the-spotted-tailed-quoll-Dasyurus-maculatus-in-north-eastern-New-South-Wales.pdf).

Dasyrus m. maculatus is, indeed, smaller-bodied than common, widespread mongooses in Africa, such as Herpestes ichneumon (https://animaldiversity.org/accounts/Herpestes_ichneumon/ and https://www.inaturalist.org/taxa/41900-Herpestes-ichneumon) and Ichneumia albicauda (https://www.inaturalist.org/taxa/41939-Ichneumia-albicauda).

Although D. m. maculatus is smaller-bodied than Felis catus, comparison of pace of life remains meaningful. This is because

• 1.8 kg and 2.6 kg are somewhat similar, and
• the direction of the difference is such that any bias would be towards the marsupial having the more rapid reproduction.

PACES OF LIFE

Please see the numerical summary below.

Dasyurus m. maculatus is slower than F. catus in

• metabolism,
• reproduction, and
• growth.

The only aspect of pace of life in which the marsupial exceeds the placental is lifespan/longevity. Dasyurus m. maculatus is far shorter-lived than F. catus, which means that the generations turn over more rapidly in this marsupial than in the carnivore.

Human body temperature is 37 degrees Celsius (https://www.ncbi.nlm.nih.gov/books/NBK331/#:~:text=Normal%20body%20temperature%20is%20considered,0.25%20to%200.5%C2%B0C.). In the marsupial, the value is 1.5 degrees less than the human value, whereas in the carnivore it is 1.5 degrees more than the human value.

The fact that D. m. maculatus runs 3 degrees C cooler than F. catus reflects a great difference to their metabolic rates.

FELIS CATUS (https://animaldiversity.org/accounts/Felis_catus/)

• Body mass: 2.6 kg (females), 4.1 kg (males)
• Metabolic rate 17.4W (based on https://animaldiversity.org/accounts/Leopardus_pardalis/)
• Body temperature: 38.3-39.2 degrees C
• Time from conception to female sexual maturity 65 days + 6 months (9-12 months in wild ancestor) = 248 days
• Number of neonates per birth: mean 4-6 (3.7 in wild ancestor) maximum 9 (https://www.dutch.com/blogs/cats/how-many-is-litter-of-kittens)
• Number of births per year: up to 3 (1 in wild ancestor)
• Lifespan: mean 14 years, maximum 38 or possibly 42 years (15 years, >30 years in wild ancestor) (https://en.wikipedia.org/wiki/Aging_in_cats)

DASYURUS MACULATUS MACULATUS (https://en.wikipedia.org/wiki/Tiger_quoll and https://animaldiversity.org/accounts/Dasyurus_maculatus/ and https://aszk.org.au/wp-content/uploads/2020/06/Spotted-Tailed-Quoll-Dasyurus-maculatus-ODonnell-J.-2014.pdf)

• Body mass: 1.8 kg (females), 3.5 kg (males) (also see Table 1 on page 20 of https://aszk.org.au/wp-content/uploads/2020/06/Spotted-Tailed-Quoll-Dasyurus-maculatus-ODonnell-J.-2014.pdf)
• Metabolic rate 3.142W 0.001763 w/g (also see Table 2 on page 21 of https://aszk.org.au/wp-content/uploads/2020/06/Spotted-Tailed-Quoll-Dasyurus-maculatus-ODonnell-J.-2014.pdf)
• Body temperature: 35-36.5 degrees C
• Time from conception to female sexual maturity: 21 days + 340 days = 361 days
• Number of neonates per birth: mean 5, range 2-6
• Number of births per year: one
• Lifespan: mean 4 years, maximum 6 years 3 months

DISCUSSION

Australia is the flattest and driest of the vegetated continents.

As a result of its tectonic stability, the soils of Australia are 'senile', with few exceptions (https://soe.dcceew.gov.au/land/environment/soil#:~:text=Overall%2C%20Australian%20soils%20are%20deeply,recent%20clearing%20and%20land%20conversions.).

The habitat of Dasyurus m. maculatus in southeastern Australia has relatively copious and reliable rainfall. So, limitations on drinking water hardly provide an adaptive explanation for its slow pace of life.

However, the nutrient-poverty/dystrophy of its habitat - and the associated evergreen woodiness of the vegetation - has profound explanatory power.

In Australia before European arrival, there was presumably no niche for felids, because the sustainable rate of offtake of prey by mammalian predators was limited.

Under these conditions, a marsupial carnivore, with its limited pace of life, was adaptive.

With European settlement, the land was farmed and the ecosystem changed. This boosted the supply of prey - including other introduced species of fecund mammals, particularly Mus musculus (https://www.inaturalist.org/taxa/44705-Mus-musculus) and Oryctolagus cuniculus (https://www.inaturalist.org/taxa/43151-Oryctolagus-cuniculus).

Anthropogenic intervention created niches for Carnivora in Australia.

Given this conceptual framework of a poor continent with according adaptation of 'metabolic poverty', the main surprise in the information tabled above is the fact that the marsupial is so much shorter-lived than the eutherian.

For example, the red kangaroo (Osphranter rufus, https://racinezoo.org/red-kangaroo-fact-sheet and https://en.wikipedia.org/wiki/Red_kangaroo) lives up to 25 years, compared to a value of only 20 years for its closest ecological counterpart, the springbok (Antidorcas marsupialis, https://genomics.senescence.info/species/entry.php?species=Antidorcas_marsupialis#:~:text=In%20the%20wild%2C%20these%20animals,is%2019.8%20years%20%5B0671%5D. and https://en.wikipedia.org/wiki/Springbok). This is consistent with, and proportional to, the difference in pace of life: macropod marsupials metabolise, breed, and grow slowly compared to bovid ruminants.

However, dasyurids (Dasyuridae) do not conform to this pattern.

Instead, an abbreviated lifespan is a tendency in the whole family to which D. m. maculatus belongs (https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/jzo.12672 and https://animaldiversity.org/accounts/Sarcophilus_harrisii/ and https://en.wikipedia.org/wiki/Semelparity_and_iteroparity and https://www.researchgate.net/publication/303757399_Evolution_of_semelparity_in_male_dasyurid_marsupials_a_critique_and_an_hypothesis_of_sperm_competition and https://www.jstor.org/stable/2459950).

Dear readers, how can this anomaly - of slow pace of life combined with reduced longevity - be explained, in adaptive terms (please see https://royalsocietypublishing.org/doi/10.1098/rspb.2018.1291)?

Posted on 26 July, 2023 22:34 by milewski