Nutrition Archives - The Sciku Project

February 17, 2022February 17, 2022

Fussy Eaters

When it comes to food,
a devil may indeed care.
Picky scavengers.

Scavengers are opportunists, feeding whenever and on whatever they can. If an animal relies primarily on scavenging (instead of hunting) then food is not guaranteed and so it’s important to feed when they can. As a result, scavengers shouldn’t be picky eaters.

Yet recent research by Lewis et al. (2022) suggests that the Tasmanian devil may buck these expectations. The researchers took whisker samples from devils caught around Tasmania and analysed the stable isotopes present in them to determine what the devils had been eating.

Rather than seeing the generalised diet typical of a scavenger, the researchers found that most Tasmanian devils are actually dietary specialists, preferring to feed on specific foods (for example birds, wallabies or possums). Curiously, heavier devils were more likely to show this specialisation in feeding behaviour, although the reasons for this are as yet unknown.

So why are Tasmanian devils different from all other scavengers?

It may be because there are no larger predators to compete with in Tasmania – their main competition is each other. Medium-sized mammals, such as wallabies and possum, are common victims of road collisions which may mean that there’s an abundance of carcasses of these species for devils to choose from, which combined with reduced competition enables dietary specialisation.

Further reading: http://dx.doi.org/10.1002/ECE3.8338

December 7, 2018December 7, 2018

Spider milk

Unexpected milk –
not a mammalian trait?
Lactating spider.

Caring mothers aren’t the first thing that spring to mind when you think about spiders. Yet plenty of evidence exists of female spiders providing food for their young and protecting their offspring. A recent and very surprising example of arachnid maternal care comes from a species of ant-mimicking jumping spider.

Chen et al (2018) observed female spiders secreting a nutritious milk-like substance, which the offspring first consume from the floor of the nest and once they are a bit older directly from the mother herself. Through a careful set of experiments the researchers found that the spiderlings are entirely dependent on this ‘milk’ for survival, and that there are still huge survival benefits to it even once they are old enough to forage independently.

Milk provision was once seen as an exclusively mammalian trait but this research adds to growing evidence that the practice is more widespread across animal taxa than previously thought.

Original research: http://dx.doi.org/10.1126/science.aat3692

February 6, 2018February 6, 2018

On a knife edge

Life on a knife edge:

The metabolic demands

facing polar bears.

Polar bears rely on marine mammals such as seals which are high-fat prey. Despite the richness of their diet however, new research suggests that a reduction in the prey availability can have severe consequences on polar bear survival.

Pagano et al (2018) monitored nine free-ranging female polar bears over 2 years, measuring their metabolic rates, daily activity patterns, body condition and foraging success. They found that more than half of the bears had an energy deficit resulting from a high metabolic rate (1.6 times higher than previously assumed) and a low intake of the high-fat prey. As fragmentation of sea ice continues and seals become harder to catch the high metabolic requirements of polar bears is likely to become increasingly catastrophic for the species.

Original research: https://doi.org/10.1126/science.aan8677

September 22, 2017December 11, 2017

Do creepy-crawlies suffer?

Do creepy-crawlies

suffer as live food? Is this

a welfare concern?

Invertebrates are often used as live food for other animals in captivity (for example geckos are often fed live crickets). Increasingly there are suggestions that some invertebrate species may be able to experience a sensation of pain and may have higher cognitive functions such as emotions and learning. As a result, should we be considering the ethical and welfare issues associated with using invertebrates as live prey?

Keller (2017) has published a review of the latest research into invertebrates and how institutes using live prey might consider and act on any welfare implications. Since there is mounting evidence that some invertebrate species can suffer, perhaps it would be best to stop all live prey feeding? But this response has its own problems: live prey feeding provides enrichment to captive species and many captive species will not feed if the food item is dead.

September 11, 2017September 11, 2017

Lurking inside intestines

The fountain of youth

lurking inside intestines:

Microbiota.

Gut microbes are important for digestion, nutrition and immunity, and gut microflora may impact on life expectancy. Young African turquoise killifish have diverse microbial communities but this diversity decreases over time. By feeding middle-aged killifish the microbes from younger fish, Smith et al (2017) found that the older fish lived longer and were more active in later life. Manipulating gut microbe composition may therefore be a way of delaying diseases related to ageing.

July 25, 2017August 30, 2017

Tiny passengers

What will satisfy

these cravings? I should ask my

tiny passengers.

Choosing what and how much to eat is crucial as even those nutrients that are normally beneficial can be harmful if consumed excessively. But the mechanism for how animals regulate the amount they eat isn’t always clear.

The common fruit fly develops a strong appetite for amino acid-rich food if fed a diet lacking in certain essential amino acids, and the fly’s reproductive effort will also decrease. However, this change in appetite and reproduction is suppressed if the fly has certain species of gut bacteria. Interestingly, when given the choice fruit flies will eat more food that contains these bacteria than food that doesn’t suggesting an ability of the flies to direct their own gut bacterial microbiome.

How the bacteria influence fruit fly behaviour and physiology is uncertain but results suggest that it is not down to the bacteria producing the missing amino acids for the flies or that the flies are consuming the bacteria themselves. Possible explanations are that the bacteria secrete metabolites that help the flies use their remaining amino acids more effectively or that the bacteria directly modulate the flies own nutrient sensing pathways so that the flies don’t recognise a decrease in amino acids. Leitão-Gonçalves et al, 2017.