Tag Archives: mongoose

Mongooses remember when their friends helped them — and help them back

It’s another one of those things that was once thought to be exclusively human but has since been shown to be present in the animal world: dwarf mongooses remember previous cooperative acts by their groupmates and reward them later, according to new work by University of Bristol researchers

Image via Wikipedia.

Don’t let their cute fluffy appearance deceive you — the dwarf mongoose (Helogale parvula) is a predator. It’s Africa’s smallest predator, but still. They live in very social groups of up to 30 individuals, with a strict hierarchy among same-sexed animals within a group, headed by the dominant pair (normally the oldest group members). All group members cooperate in helping to rear the pups and in guarding the group against predators.

Dwarf mongooses also maintain an interesting mutually advantageous relationship with hornbills, in which hornbills seek out the mongooses in order for the two species to forage together more successfully, and to warn each other of nearby predators. So it shouldn’t surprise anyone, really, that the dwarf mongoose is a great communicator and a very social creature. But what did surprise biologists is that not only do these creatures remember when others help them — but they also reward their helper, even after a lot of time has passed. Senior author, Professor Andy Radford from Bristol’s School of Biological Sciences, said:

“Humans frequently trade goods and can track the amount they owe using memories of past exchanges. While nonhuman animals are also known to be capable of trading cooperative acts immediately for one another, more contentious is the possibility that there can be delayed rewards.”

Dwarf mongoose acting as a sentinel (raised guard) a cooperative act that is later rewarded by grooming from groupmates. Image credits: Shannon Wild.

Until now, this type of behavior has only in primate populations, and studies have generally focused on captive populations. Lead author, Dr. Julie Kern, also from Bristol, added:

“There have been hardly any suitable experimental tests on wild animals, especially non-primates. By working with groups of dwarf mongooses habituated to our close presence, we could collect detailed observations and conduct experimental manipulations in natural conditions.”

The study also revealed one of the first cross-commodity trading, whereby individuals reward one type of good or service with another. In this case, grooming was traded for sentinel behavior (depicted above), which involves adopting a high position and keeping a lookout for danger, warning groupmates with alarm calls if something’s wrong.

[Also Read: For banded mongooses, ‘cultural inheritance’ decides what’s for dinner]

Researchers had witnessed this type of behavior several times, but proving a cause-effect relationship was quite tricky, so researchers set up a creative experiment. Professor Radford explains:

“Over three-hour periods when groups were foraging, we simulated extra sentinel behaviour by a subordinate group member using playbacks of its surveillance calls–vocalisations given to announce it is performing this duty. At the sleeping burrow that evening, we monitored all grooming events, especially those received by the individual who had had their sentinel contribution upregulated.”

They found that on days when an individual was perceived to conduct more sentinel duty, it received more evening grooming from groupmates than on regular days (when its foraging calls had been played back during the preceding foraging session). Furthermore, they found that the grooming needn’t occur immediately — sometimes, it took a while before the reward came.

It might seem like the two services don’t quite match up, as being a sentinel seems much harder and more important than being a groomer, but grooming has long been considered an important tradable commodity in social species, being used as a reward or as a sign of affection in various contexts.

Journal Reference: ‘Experimental evidence for delayed contingent cooperation among wild dwarf mongooses’ by J.M. Kern and A.N. Radford in Proceedings of the National Academy of Sciences, USA.

For banded mongooses, ‘cultural inheritance’ decides what’s for dinner

It’s no surprise that for humans, culture decides a vast majority of our preferences: from the language we speak to the food we like. But surprisingly, animals also make decisions based on cultural preferences.

Image credits: Feargus Cooney.

Why do we do the things that we do? We might think it’s in our genes or it’s just who we are (and that’s partially true), but our culture also plays an important role.

“Cultural inheritance, the transmission of socially learned information across generations, is a huge influence on human behavior: we behave the way we do not just because of our genes, but also because of what we learn from parents, teachers, and cultural role models,” says Michael Cant from the University of Exeter. “It is less well appreciated that cultural inheritance is a major force shaping behavior in a wide range of non-human animals, from insects to apes.”

Intriguingly, this is not something limited to humans — or to primates, for that matter. Among others, whales and birds have been shown to exhibit cultural inheritance, and it makes a lot of sense: parents pass information off to their offspring, helping them adapt to the world more quickly and waste less energy learning useful skills.

Along with these useful skills, parents also pass down preference, but this has been notoriously difficult to study in mammals. In a new study, Cant and colleagues had to take advantage of a quirk in banded mongoose society. Banded mongooses live in highly cooperative groups. The groups trust other members of the society so much that offspring form exclusive one-to-one caring relationships with unrelated adults — called escorts. Escorts aren’t really related to the offspring, it’s just a case of simple fostering.

Cant and his team closely followed this relationship and surprisingly, found that the younglings tend to follow the foraging behavior of the escorts who took care of them — not their parents. In other words, the mongoose exhibit cultural, and not genetic, inheritance.

“It was a big surprise to discover that foraging behavior learned in the first three months of life lasts a lifetime,” Cant says. “To illustrate, our data show that even middle-aged mongooses are still copying the foraging behavior of the escort that looked after them for a short period when they were a small pup, years before. This is pretty remarkable, since we have no evidence that pups and escorts preferentially hang out together after pups become independent.”

The study seems to suggest that cultural inheritance may be a much more pervasive behavior than we thought. It doesn’t require a large brain or mental complexity, Cant says, and might, therefore, be much more common than we once thought it to be.

Ultimately, researchers say they’d like “to understand not just how different early life influences on development work in social organisms, but why they evolved.”

Journal Reference: Sheppard & Marshall et al.: “Decoupling of Genetic and Cultural Inheritance in a Wild Mammal”. Current Biology. https://www.cell.com/current-biology/fulltext/S0960-9822(18)30603-1

caribbean-skinks

24 new lizard species discovered in the Caribbean – already faced with extinction

A team of researchers at Penn State University has identified 24 new species of skinks, a subspecies of lizards, native to the Caribbean Islands, turning the region’s fauna from one of the smallest lizard groups in the world to one of the largest. However, half of these new species are considered already extinct or very close to extinction, while the other half is threatened by extinction. The scientists blame the mongoose for Caribbean skink holocaust, a predatory mammal introduced by farmers to control rats in sugarcane fields during the late 19th century.

caribbean-skinks

About 130 new species of reptiles are added each year to the world species count, however this was the first time since the 1800s when more than 20 new species had been added and described in a single paper. In total, the Penn State scientists looked at 39 skink species, of which six were already recognized, nine had already been described and given names but were considered invalid until now, and the rest are absolutely new species. Why did it take so long for these many skink species to be identified by scientists when the region is booming with humans and numerous scientific expeditions? The scientists explain that first of all, because of the dwindling number of surviving specimens, the newly found skink species are elusive and rarely seen, and secondly, the variations between species are very subtle and hard to notice, hence it’s very common to believe a specimen is part of an already well known species, when in fact it might be part of an entirely unidentified species. Some of the new species are six times larger in body size than other species in the new fauna.

“Now, one of the smallest groups of lizards in this region of the world has become one of the largest groups,” Hedges said. “We were completely surprised to find what amounts to a new fauna, with co-occurring species and different ecological types.”

The team of researchers, lead by Blair Hedges, professor of biology at Penn State University, used DNA sequences to identify the new animal species, but most of the taxonomic information, such as counts and shapes of scales, came from examination of the animals themselves either of museum specimens or live ones.

Not your ordinary backyard gecko

It’s believed the Caribbean skinks surfaced in the region some 18 million years ago after  from Africa by floating on mats of vegetation. That may be impressive, however what makes these reptiles truly special is the fact that females  produce a human-like placenta, which is an organ that directly connects the growing offspring to the maternal tissues that provide nutrients.

“While there are other lizards that give live birth, only a fraction of the lizards known as skinks make a placenta and gestate offspring for up to one year,” Hedges said.

This lengthy gestation period also gave their predators a hefty advantage, as gestation females are considerably slower and easier to catch.

“The mongoose is the predator we believe is responsible for many of the species’ close-to-extinction status in the Caribbean,” Hedges said. “Our data show that the mongoose, which was introduced from India in 1872 and spread around the islands over the next three decades, has nearly exterminated this entire reptile fauna, which had gone largely unnoticed by scientists and conservationists until now.”

“By 1900, less than 50 percent of those mongoose islands still had their skinks, and the loss has continued to this day,” Hedges said.

The research team reports on the newly discovered skinks in a 245-page article published today (April 30) in the journal Zootaxa.

source: Penn State Live