Predation 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

March 19, 2021March 19, 2021

Rigs to Reefs

Oh puffing pig fish –
torn between disturbance and
piscine temptations.

Noise pollution from oil and gas drilling platforms can have huge negative impacts upon marine life. However, such rigs can also act as artificial reefs, providing shelter and a hard substrate for predators and prey alike. Moreover trawling isn’t permitted close to rigs, meaning that the seabeds around them are mostly untouched.

Harbour porpoises, Phocoena phocoena, have previously been shown to change their behaviour or avoid areas as a result of unnatural noise levels. Yet a recent study by Tubbert Clausen et al. (2021) has revealed that the temptations of high prey availability can overcome such affects. The team use 21 acoustic loggers, placed on the seabed for up to 2 years to monitor noise levels and harbour porpoise activity.

They found that despite the high noise levels from the largest rig in the Danish North Sea, the porpoises were still found close to the rig, emitting echolocation noises that indicate they were hunting for fish. The platform’s artificial reef effect appeared to increase fish numbers which drew the porpoises closer.

The findings suggest that as platforms come to the end of their lifespans, they could be partially left in place to continue acting as artificial reefs – the rigs-to-reefs concept.

The first line of the sciku refers to two names for the harbour porpoise:

– The ‘pig fish’ from the Medieval Latin porcopiscus, a compound of porcus (pig) and piscus (fish).

– The ‘puffing pig’ which comes from the noise the porpoises makes when surfacing to breathe.

Original research: https://doi.org/10.1002/2688-8319.12055

September 12, 2019September 12, 2019

Tiny predator

Cambrian fossil,
your pincers – a coat of arms.
Ancient arachnid.

The Burgess Shale in the Canadian Rockies has some of the most complete and well preserved fossils found anywhere in the world, allowing researchers to gain huge insights into life millions of years ago during the middle Cambrian period.

Now a new species has been described that illuminates the early development of chelicerate – a group of over 115,000 species that contains spiders, scorpions and horseshoe crabs.

In their paper Aria & Caron (2019) describe the morphology of Mollisonia plenovenatrix, including robust but short chelicerae (pincers) that were located between the animal’s eyes, in front of its mouth. These are the predecessors of the pincers that spiders and scorpions use to kill, hold and cut their prey.

It’s likely that the species hunted close to the sea floor, using long walking legs and other sensory limbs to detect prey. The finding suggests that the origin of the chelicerate must be earlier in the Cambrian period and that the group must have rapidly expanded to fill an underutilised ecological niche.

A note about the sciku: For the sake of the poem I have simplified chelicerate to arachnids. Lead author Cédric Aria has described the pincers (chelicerae) as the ‘coat of arms’ of the chelicerate which felt suitably poetic.

Original research: http://dx.doi.org/10.1038/s41586-019-1525-4

September 7, 2018September 7, 2018

No catch-22

Does the protected

lion eat conserved zebra?

Phew! No catch-22!

Recovering predator populations as a result of conservation work can result in impacts on their prey species populations, causing issues if those prey species are themselves endangered. One case in particular is whether lions exert top-down pressure on Grevy’s zebra in Kenya – does the recovery plan of one species negatively affect the conservation of another?

A study by O’Brien et al (2018) suggests we need not worry in this case – working in Laikipia County in Kenya the researchers found that lions were less likely to prey on Grevy’s zebra than expected. In fact, population trends suggest that the Grevy’s zebra population in Kenya may be stabilising. The researchers conclude that the most likely threat to Grevy’s zebra are competition for grass with Plain’s zebra and the impact of livestock.

Original research: http://dx.doi.org/10.1371/journal.pone.0201983

August 31, 2018January 29, 2021

Fluttering by at dusk by Roy McGhie

Fluttering by at dusk,

dawn, and in between.

Crop diversity!

Recent research by Olimpi & Philpott (2018) concludes that crop diversity as a management practice drives bat activity, and that crop diversity and less frequent pesticide use increase bats’ insect prey populations. The study notes that this could be a useful management tool where other options, such as hedgerow or tree management, are not available.

Original research: https://doi.org/10.1016/j.agee.2018.06.008

Roy McGhie works for Natural England as an Uplands Advisor. You can connect with him on LinkedIn here. If you enjoyed his sciku, check out his previous poems Ghost Ponds, A Heady Mixture and Hedgerow Snuffling.

May 17, 2018May 17, 2018

You aren’t one of us.

Help! Help! Predator!

Guys, why aren’t you helping me?

You aren’t one of us.

Jackdaws respond to anti-predator calls to join the caller in mobbing the predator and driving it away. Yet researchers have now found that who the caller is will affect the level of response.

In playback experiments Woods et al (2018) that the highest response was to nestbox residents who would be highly familiar with the caller. The level of response to an anti-predator call diminished as familiarity decreased from colony members to non-colony members and then to rooks (a species that often lives alongside jackdaws).

Original research: http://dx.doi.org/10.1038/s41598-018-25793-y

November 24, 2017December 11, 2017

Dark moths by Prof Matthew J. James

Industrial soot

Biston betularia

Quo vadis dark moths?

The Peppered Moth (Biston betularia) is a classic example of evolution in action, yet in recent years Darwin’s Finches seem to have eclipsed the Peppered Moth as the textbook example of natural selection.

This sciku, written by Professor Matthew J. James, celebrates the Peppered Moth as an example of rapid natural selection and asks where the dark moths are going, Quo vadis in Latin meaning “Where are you going?”. The question refers to both the population change in moth colouration from dark to light and also implies a nostalgic deeper meaning asking where the Peppered Moth explanation of natural selection has gone in light of the present-day dominance of Darwin’s Finches.

The wild-type Peppered Moth has light wing patterns that act as effective camouflage against its common environmental background. Industrial smog from 19th century coal burning in the United Kingdom resulted in the trees upon which they rested becoming blackened by soot, making the moths stand out. As a result the population of light-winged moths plummeted due to increased predation, however numbers of the melanic mutant form (black in colour) of the species rose – this process has been termed Industrial Melanism. As the Industrial Revolution waned and levels of pollution decreased, numbers of the light-winged form of the moth rose once again. Cook & Saccheri (2013) present an interesting review of the Peppered Moth as a natural selection case study.

Original research: https://dx.doi.org/10.1038%2Fhdy.2012.92

Professor Matthew J. James is Chair in the Department of Geology at Sonoma State University, California. His recent book, Collecting Evolution, examines a scientific collecting expedition to the Galapagos Islands in 1905-06 that resulted in the concept of Darwin’s Finches being developed by David Lack in his 1947 book by that same name.

August 30, 2017August 30, 2017

Pray, are you a predator?

Have we met before?

Pray, are you a predator?

I am so naive!

Predators are a threat for most animals and gauging whether a novel species is dangerous or not can be a life or death judgment. Whilst some species may have a degree of innate predator recognition, research suggests other species require prior experience of the predator to learn of its danger.

Great and blue tits were tested with novel and familiar predators. Tits from populations familiar with both sparrowhawks and little owls reacted towards the stimuli as expected, mobbing the predators equally. But tits from populations only familiar with sparrowhawks did not treat the little owl stimulus as a threat, suggesting it wasn’t recognised as a predator. Prior experience of predator species is therefore important in great and blue tits. Carlson et al, 2017.