Ecological news and research

I have recently seen a couple of pieces of research that I think may be of interest, so I am leaving them here.

Burrowing, colonial mammals
This paper reviews the ecosystem roles placed by burrowing, colonial, herbivorous and mostly small mammals around the world. The species considered include the prairie dogs (North America), ground squirrels (North America, Eurasia and Africa), marmots (North America and Eurasia), plains vizcacha, Patagonian mara, degu (South America), pikas (Asia), ice rats, springhares (Africa), burrowing bettongs and hairy-nosed wombats (Australia).
The ecological roles played by these species include grazing, habitat creation by digging, facilitating water filtration, increasing soil nutrients, maintaining open grassland, facilitating larger grazing animals, providing shelter and breeding habitats in burrows and providing prey for a large number of predator species.
The paper finally looks at threats facing these important mammals including habitat destruction, conflicts with livestock, overexploitation, introduced species and climate change. This section also looks at the ecological consequences of the loss of these mammals and how their declines can be reversed.

The review in question is included below:
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.248.8029&rep=rep1&type=pdf

Ganges softshell turtle
This note examines the causes of unusual flocking behaviour in wintering Eurasian coots at Keoladeo in India. Unlike in Western Europe, where wintering coots form loose flocks and retreat to deep water to roost or when threatened by predators, the coots here roost on islands and forage in extremely dense flocks; when entering the water after roosting the coots did so en masse. This behaviour has been considered to be a response to attacks by eagles but several times, when large flocks of coots showed escape behaviour, no eagles were visible. This note considers that the behaviour of the coots at Keoladeo is due to an aquatic predator, most likely the Ganges softshell turtle Aspideretus gangeticus. On one occasion a coot was seen being drowned by an aquatic predator, most likely a softshell turtle.
The note includes reference to a very interesting observation from Keoladeo where two large softshell turtles were observed to pull down a full-grown albeit injured nilgai antelope, which was then attacked and eaten by a number of other turtles.
The authors suggest the dense flocking is intended to confuse aquatic predators attacking from below and also provide greater safety of numbers for coots. Dense flocking and island roosting is also recorded in other waterbirds at Keoladeo including Eurasian teal and Northern pintail.

The note in question is included below:
https://s3.amazonaws.com/academia.e...e34655945948b29f156dbd17d86ea2966bf9ffad1d134

 

Recent research on the goliath frog (Conraua goliath) along the Mpoula River in Cameroon has found that the species builds nests for its young. There are three types of nest:
Nest type 1 are rock pools cleared of detritus and leaf-litter
Nest type 2 constitutes existing washouts along the riverbank cleared of leaf-litter and/or expanded
Nest type 3 are depressions dug by the frogs into gravel riverbanks

All three nest types contained eggs and tadpoles. The nests are built to allow the young to be deposited in a site safe from river predators and fast-flowing water. The building of the nests, which can require moving large stones, is considered by the scientists here to possibly be the reason why goliath frogs grow so large.

In terms of other species potentially impacted by the frog's nest-building, several type 2 nests were found to have small fish and shrimps (Caridina evae) living in them.

The full research article is included below:
https://tandfonline.com/doi/full/10.1080/00222933.2019.1642528

 

I saw a couple of interesting articles that I figured I would include here:

Tapirs and peccaries
Research in Brazil has found that lowland tapirs and white-lipped peccaries have complementary ecological effects on forest plant diversity, with diversity higher in places where both species occur than in those areas with just one species.

The peccaries act as predators of seeds and seedlings, trampling the soil and significantly reducing understory growth in tropical forests. The tapirs have less impact on the vegetation and transport seeds in their stomachs. The scientists hypothesise that the disturbance caused by peccaries will increase the likelihood that tapir-dispersed seeds will become adult trees.

The abstract to the paper is included below:
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An article about this research is included here:
https://phys.org/news/2019-11-extinction-lowland-tapir-white-lipped-peccary.html

Vulturine guineafowl sociality
A field study of vulturine guineafowl in Kenya has found that the species has a complex multilevel society thought to only exist in mammals such as primates, elephants, giraffes and dolphins. The study of over 400 individually-marked adult guineafowl found that the birds form stable groups which would mingle with other groups at times (such as roosting) but then remain in their original group on splitting up again. The researchers believe that the guineafowl may be important in learning how complex multilevel societies evolved.

The abstract for this paper is included below:
https://www.cell.com/current-biolog...m/retrieve/pii/S0960982219312631?showall=true

The article about the research is here:
https://phys.org/news/2019-11-complex-society-vulturine-guineafowl.html

 

I also recently saw this research from a couple of years ago and thought I would put it here as well:

Aquatic and semi-aquatic herbivores
This paper reviews the ecological role of large (>10kg) aquatic and semi-aquatic herbivores including their impact on abundance and species composition of aquatic plants and their ecosystem functions. The researchers were able to split up the species into four distinct groups:
1) Fully aquatic species, either resident or migratory (Manatees, dugongs, sea turtles)
2) Semi-aquatic species that live on both water and land, either resident or migratory (Swans)
3) Resident semi-aquatic species that live in water but forage on land (Beaver, capybara, hippopotamuses)
4) Resident terrestrial species that frequent aquatic habitats (Lowland tapir, moose, marsh and swamp deer, water buffalo)

The research then looks at the different ecosystem functions each animal does - their impacts on plants, other species, nutrients and their role as physical engineers.

The paper in question can be found on the link below:
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While I was looking through papers today, I found these four research articles about four very different ecosystem engineers. I figured I would post them here:

Japanese black bear
Asiatic black bears living in central Japan create small gaps in the canopies of Mongolian oaks by breaking branches to create platforms from which acorns can be gathered. Researchers studying these gaps found that light levels down to the forest floor were much higher than in areas with intact trees and this, combined with increased numbers of pollinators using the light-filled gaps made by the bears, increased the fruits produced by fleshy-fruited plants such as roses, grapevines, dogwoods, mulberries and Chinese gooseberries which benefit both the bears and other frugivorous species.

The full research paper can be found below:
Do Small Canopy Gaps Created by Japanese Black Bears Facilitate Fruiting of Fleshy-Fruited Plants?

Woodpeckers
This paper explored whether ecosystem engineers are interchangeable for resource users depending on their habitat. The two resource users, mountain bluebirds and tree swallows, both use cavities created by Northern flickers in aspen groves - the flicker creates more holes than any of the other local woodpeckers. In more continuous forest, the tree swallow was associated strongly with both red-naped sapsucker (which creates the most holes) and hairy woodpeckers (which create few but high-quality holes) while the bluebird used mostly flicker and hairy woodpecker holes. The results of this study show that the interactions between engineer and resource user species may change with the available habitat.

The full link is available below:
Habitat-Mediated Variation in the Importance of Ecosystem Engineers for Secondary Cavity Nesters in a Nest Web

Little auk
This study looked at how little auks, the most abundant North Atlantic seabird, alter freshwater and terrestrial ecosystems around the North Water Polynya in Greenland. The presence of auk colonies was found to profoundly alter these ecosystems by providing nutrients and massively enhancing primary production. It is estimated that more than 85% of terrestrial and freshwater biomass in these areas is fuelled by marine-derived nutrients carried ashore by the auks. Little auk droppings acidify the freshwater habitats, reducing the taxonomic richness of macroinvertebrates and truncating food webs. It has been found elsewhere that reducing this flow of nutrients (for example by introduced predators predating seabirds) causes the landscape to shift from grassland to tundra. All this shows the little auk is a key ecosystem engineer in large areas of the Arctic.

The full reference can be read below:
https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2016.2572

Longhorn beetle
This study examined the ecosystem effects of the stem-boring longhorn beetle Oncideres albomarginata chamela in a tropical dry forest in Mexico. This species detaches small branches from trees and cuts notches into them for egg-laying. By placing these detached and cut branches into net bags and comparing them against artificially-manipulated and unmanipulated branches, the researchers found 28,301 secondary colonisers emerging from the beetle-cut branches. The secondary colonisers were mostly other wood-feeding beetles along with predatory beetles and parasitic wasps. Overall, these stem-boring beetles were responsible for nearly 95% of the abundance of these secondary colonisers and 82% of the species richness. These results show this species of beetle is a keystone ecosystem engineer that structures a large community of arthropods.

The full paper can be read on the link below:
Insects as Stem Engineers: Interactions Mediated by the Twig-Girdler Oncideres albomarginata chamela Enhance Arthropod Diversity

 

I have recently seen this research that I thought was interesting enough to warrant posting here.

A camera trapping study at nine harpy eagle nests (a tenth was found but the camera failed to work) in Brazil has recorded the extent of nest use by other vertebrates. As well as the harpy eagles, twenty-seven other species were documented at the nests; six of these were mammals and twenty-one were birds.

Twenty of the visiting species fell within the limits of recorded harpy eagle prey size and ten are known prey species. Two species were observed in direct interactions with harpy eagles - a tayra that visited a nest aggressively displaced the courting adults while a hooded capuchin foraging at the nest was killed by an eagle. Even though several visiting species were predators, no eggs or chicks were harmed. Indeed no species visited the nests at all during the incubation and nestling stages.

The nest structure and accumulation of decaying leaves and carrion encouraged the growth of epiphytic plants and provided an ideal microhabitat for invertebrates. It was these that attracted foraging Southern tamanduas, the most common visitor of harpy eagle nests. Also documented was possible commensalism between the eagles and both king and greater yellow-headed vultures, which scavenged prey remains in the nest.

This research suggests that the harpy eagle could be an ecosystem engineer in South America, providing habitat and resources to a large number of other species.

The full paper is available here:
https://www.researchgate.net/profil...species-Interactions-Under-Predation-Risk.pdf

 

A most interesting article.

 

I have seen this piece of research from 2017 that I thought was interesting enough to warrant sharing here.

The Southern African silkmoth Gonometa postica has been found to be an ecosystem engineer, providing shelter to other invertebrates with its abandoned cocoons. The main invertebrates that used cocoons were ants, primarily the Crematogaster ants that normally occupy swollen galls in acacia trees. While ants occupied just under half (48%) of cocoons, those that were not used by ants were instead used by spiders, beetles or other caterpillars. The relationship between the ants and silkmoths is interesting, as the ants will attack and dislodge the moth caterpillars from the tree but can benefit if the caterpillar survives to pupate. While this study was conducted in South Africa, this relationship has also been observed in Namibia and is possibly widespread across the moth's range.

This discovery may have implications for the harvesting of wild cocoons for silk manufacture. It could result in reduced numbers of ants on acacia trees and reduce their protection against other insect herbivores. To combat negative effects, the researchers recommend either:
a) That collectors leave some cocoons on the trees in order to provide nest sites for invertebrates.
b) If cocoon collecting cannot be regulated, there should be a rolling-out and improvement of semi-captive and artificial rearing techniques

The paper is included here:
Empty Gonometa postica cocoons function as nest sites and shelters for arboreal ants - ScienceDirect

 

I have seen recently a couple of bits of research about the unusual diets of some aquatic mammals, which I am posting here:

Baikal seals
Scientists have recently found that Baikal seals mostly feed on the amphipod Macrohectopus branickii, rather than fish as previously believed. While previous studies involved looking at seal stomach contents, this one placed cameras onto the animals and found that, on average, they consumed 57 amphipods per dive and hunted one every 2.5 seconds. To allow them to feed on such a diet, the Baikal seal has evolved the most specialised filter-feeding teeth of all Northern seals and the tiny size of the seals means they can achieve a net energy gain by feeding on amphipods. It is thought by the scientists that this diet is part of the reason why the Baikal seal is doing comparatively well compared to many other seals that are struggling due to fish declines.

An article about the research is included here:
https://phys.org/news/2020-11-mystery-siberian-freshwater-food-choice.html

The abstract for the paper is included here:
Ultrahigh foraging rates of Baikal seals make tiny endemic amphipods profitable in Lake Baikal

African manatees
While this research is a lot older (from 2014) I first noticed the information in a news item from early this year. A study into African manatee diets in West and Central Africa has found that the species is omnivorous throughout its range. In Gabon, where there is a high year-round richness of aquatic plants, around 10% of the diet is of animal origin, mostly consisting of hermit crabs and similar bottom-dwelling invertebrates. In Senegal, which has a much lower plant diversity and a pronounced dry season, the amount of animal prey can be up to 50%. These animal foods were comprised of molluscs and fishes. This high prevalence of animal prey may be due to the loss of vegetation such as seagrasses and mangrove swamps and also due to damming making some prey more available. However, interviews with people throughout the manatee's range seem to suggest that fish-eating is a common behaviour widespread across Western and Central Africa.

The article about the research is included here:
African manatees omnivorous - new study sheds light on manatee diet

The full paper (in dissertation format) can be read here:
https://www.researchgate.net/profil...E-AFRICAN-MANATEE-Trichechus-senegalensis.pdf

 

Recent research has found that two species of Australian monitor lizard, the yellow-spotted monitor Varanus panoptes and Gould's monitor Varanus gouldii, should be regarded as ecosystem engineers.

Both species create warrens in which they lay their eggs, some of which can be thirteen feet deep - the deepest known vertebrate burrows. The soil they excavate create germination sites for plants but the main topic of this research was use of the warrens by other animal species. A wide range of animals, including other reptiles, frogs, insects and marsupial mammals, use the burrows as shelter. An article about the research says that, in total, '747 individual species of 28 types of vertebrate were found'. Some animals use the warrens more at certain times of the year - frogs hibernate in them during the winter dry season, with the researchers finding 418 individual frogs in one warren.

A concern is that, as monitor lizards decline in Australia due to poisoning by cane toads, these important habitat features may disappear.

Research will now be expanded to include the perentie Varanus giganteus, another large monitor that nests at great depth in Australian deserts, to determine if they are also ecosystem engineers. The researchers will also look at how climate warming will impact the facilitation of these animal communities.

An article about the research is here:
https://phys.org/news/2020-12-lizard-regarded-ecosystem.html

An abstract for the paper is here:
Ecosystem engineering by deep-nesting monitor lizards - PubMed

 

I have recently seen two interesting pieces of research about hunting behaviour in different species that I will post here:

1. Volta's electric eel
Recent observations of the newly-discovered Volta's electric eel Electrophorus voltai have found that they hunt socially; observations made at the mouth of a small lake along the Iriri River of Brazil showed that they formed aggregations of over 100 individuals and herd small fish such as tetras into tight balls. Between 2 and 10 individual eels then deliver a simultaneous shock to stun large numbers of fish that the eels can then collect. Another predator, a peacock bass cichlid Cichla melaniae, was observed to opportunistically feed on stunned fish.

The research paper can be found here (videos of the hunting behaviour are included under the 'Supporting Information' dropdown menu at the bottom of the page):
https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.7121

2. Madagascar huntsman spider
A more recent observation from northeastern Madagascar concerns a huntsman spider Damastes sp. seen feeding on a tree frog Heterixalus andrakata inside a retreat made from two leaves partially woven together. Several other spiders of the same species were seen using similar shelters. While more studies will be required to confirm, the researchers believe the woven retreats could be constructed to serve as traps specifically for tree frogs, which enter them to find shade and cover.

The research paper can be found here:
https://onlinelibrary.wiley.com/doi/10.1002/ece3.7102

 

Quite an interesting bit of research I have just seen, about using frugivorous animals to restore degraded forests in Brazil.

The research aimed to find out if using the natural dispersal of seeds by native animals was more effective than planting seedlings or sowing seeds. To do this, seeds of native Cecropia hololeuca were embedded into the flesh of commercially-available native fruits, which were then offered from feeders. At least 24 generalist species of terrestrial mammals, bats and birds removed fruit from the feeders. More research will be needed to determine if the success rate of seed growth is higher for this method, called induced seed dispersal, than for other reforestation methods.

An article about the method (including a video) is included here:
Fruit-eating, seed-pooping animals can help restore degraded forests

The abstract for the actual study is included here:
https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2664.13731

 

I have recently seen these two linked studies, about how wolves affect the ecosystem in northern Minnesota.

The first study found that, by killing dispersing beavers, wolves are able to alter the creation of wetlands without changing the population or behaviour of the beavers. When the dispersing beaver is killed it is unable to maintain dams which soon begin to fail - the researchers estimated that wolves altered the establishment of about 88 ponds each year and affected the storage of over 51 million gallons of water annually. Further studies are needed on how the creation of habitat patchiness by wolves could affect other species in the ecosystem.

An article about this paper is included here:
https://phys.org/news/2020-11-wolves-wetland-creation-recolonization-ecosystem.html

The full paper is included here:
Outsized effect of predation: Wolves alter wetland creation and recolonization by killing ecosystem engineers | Science Advances

The second study looked at how wolves actually captured beavers, as they are often considered to be pursuit hunters. By studying areas where wolves capture beavers, they found that wolves set ambush points near beaver trails. This study is one of the first-ever to record a predator setting an ambush downwind of its prey; because beavers have such a poor sense of eyesight, wolves were able to choose ambush sites within a few feet of where beavers were active provided they were downwind. On average, each ambush stakeout lasted for 4 hours but they often waited 12 hours or more and one wolf was recorded waiting for 30 hours.

An article about this paper is included here:
https://phys.org/news/2021-02-uncover-hidden-tactics-wolves-minnesota.html

The abstract for the paper is included here:
Wolves choose ambushing locations to counter and capitalize on the sensory abilities of their prey

 

Another unusual predatory behaviour that has only recently been described - three species of kukri snakes in Southeast Asia (Oligodon fasciolatus, O. formosanus and O. ocellatus) have been observed killing and eating large amphibians such as banded bullfrogs and black-spined toads by biting through the abdomen and tearing out and eating the organs. It is thought that this behaviour has evolved to allow the kukri snake to feed on larger prey than it could otherwise normally swallow.

An article about the observations are included here:
https://phys.org/news/2021-02-unique-behavior-asian-kukri-snakes.html

The full paper is included here:
Gruesome twosome kukri rippers: Oligodon formosanus (Günther, 1872) and O. fasciolatus (Günther, 1864) eat Kaloula pulchra Gray, 1831 either by eviscerating or swallowing whole

 

Research on Phillip Island has found that the endemic giant centipedes Cormocephalus coynei are key to the nutrient cycling of their ecosystem. On the island, 52% of the diet consists of invertebrates and 48% consists of vertebrates including skinks and geckos, marine fish regurgitates by seabirds and the chicks of black-winged petrels Pterodroma nigripennis - this is the first ever study to record centipede predation on seabirds.

Annual predation rates on seabird chicks was between 11 and 19.6%, meaning that 2,109 to 3,724 petrel chicks may be predated annually by the centipedes.

The killing of the chicks on land helps add marine nutrients to the nutrient pool in the food web and, because the petrels are a long-lived species that only breeds once a year, the centipedes are also able to reduce the reproductive output of larger vertebrates.

An article about the research is included here:
https://phys.org/news/2021-08-giant-bird-eating-centipedes-existand-theyre.html

The full paper is included below:
https://www.journals.uchicago.edu/doi/10.1086/715702

 

A recent study has confirmed that the Chinese pangolin is an ecosystem engineer, with its burrows serving as an important habitat feature for other species.

The survey of pangolin burrows, which took place in 2020 and used motion-sensitive camera traps, recorded 37 commensal species. These consisted of 14 species of mammal, 17 of bird, 4 of reptile and 2 of invertebrate. The most common burrow visitors were small mice, with a total of 220 visits recorded (comprising about 40% of visits). These were followed by the silver pheasant (66 visits), squirrels (50 visits) and the Chinese ferret-badger (33 visits). Considered central to the community of animals that congregate around pangolin burrows are the predators, including Burmese python, spotted linsang and leopard cat.

The paper is rather confusing, as it mixes information about the pangolin study with a more general overview of burrowing ecosystem engineers. There may be more interesting things I missed on my read-through.

The paper can be found in the link below:
https://www.researchgate.net/public..._of_Chinese_Pangolin_as_an_Ecosystem_Engineer

 

Another bit of research about pangolins as ecosystem engineers, this time looking at the animals that share burrows made by giant pangolins in Gabon. In total, twelve burrows were investigated.

The pangolins dig complex, interlacing underground networks with up to ten different entrances. They can span an area of 75 square metres, are up to four metres deep and tunnels can be up to thirty metres long. Galleries intersect to form large ovoid nesting chambers.

Many other animal species were observed using giant pangolin burrows. African rock pythons were seen in two burrows; one used the burrow as a nest while the pangolin was still occupying it, although the pangolin used a separate chamber.

Brush-tailed porcupines and white-bellied pangolins periodically occupied giant pangolin burrows, sometimes simultaneously to the giant pangolin. At night, small rodents, genets and mongooses (the marsh mongoose is specifically mentioned) were also often seen in burrows.

In nine of the investigated burrows, bats were found - most were microbats, with Old World leaf-nosed bats (Hipposideridae - including Noack's roundleaf bat Hipposideros ruber), sac-winged bats (Emballonuridae) and bent-winged bats (Miniopterus) identified. On one occasion, a dwarf epauletted bat was also found in one of the burrows. The scientists in this study consider this to be a potential crossover point for diseases between bats and pangolins.

The research can be found in the link below:
Pangolins and bats living together in underground burrows in Lopé National Park, Gabon

 

Some recent research has shown how two similar species of dolphin - the Australian snubfin (Orcaella heinsohni) and humpback dolphins (Sousa sahulensis) - are able to coexist off the east coast of Queensland, as both species are very ecologically similar: they each occur in small populations of typically fewer than 150 individuals, show a high degree of overlap in habitat use, are active at the same time of day and often occur in mixed groups.

By comparing the isotopes found in the skin taken from live dolphins, the research has found that while both species feed at a similar trophic level and rely on similar basic food sources, there are subtle differences that may promote their coexistence. The snubfin dolphins forage on a slightly wider variety of prey while the humpback dolphins forage in a wider range of habitats.

An article about the research can be seen here:
https://phys.org/news/2022-08-species-dolphins-coexist-australia.html

The research paper itself can be seen here:
https://onlinelibrary.wiley.com/doi/10.1002/ece3.8937