Tag: behaviour

Accidental tree wound reveals novel symbiotic behavior

Despite significant movement restrictions during the first wave of the pandemic in Panama City, a group of curious high school students roamed their neighborhood drilling holes into Cecropia trees and documenting how Azteca alfari ants responded to damage to their host plant.

During the pandemic, five curious high school students accidentally discovered how Azteca alfari ants respond to damage to their Cecropia host trees. Photo by Donna Conlon

One afternoon, during the early days of the COVID-19 pandemic in Panama, a bored teenager with a slingshot and a clay ball accidentally shot entry and exit holes in a Cecropia tree trunk. These are “ant-plant” trees, which famously cooperate with fierce Azteca ants; the trees provide shelter and food to the ants, and in exchange the ants defend their leaves against herbivores. The next morning, to his surprise, the Azteca alfari ants living within the Cecropia trunk had patched up the wound.

This unexpected occurrence drove five curious high school students, with time on their hands, to participate in the Smithsonian Tropical Research Institute’s (STRI) volunteer program, and they enlisted STRI scientist William T. Wcislo’s help in devising their experiment. Despite significant movement restrictions during the first wave of the pandemic, they roamed their neighborhood drilling holes into Cecropia trees and documenting the ants’ responses to the damage.

They found that as soon as the plants had holes drilled into them, the ants ran to the wound area and began patching it up. Within 2.5 hours, the size of the hole had been significantly reduced and it was often completely repaired within 24 hours.

Although some Azteca ants are known to defend their Cecropia host plants against herbivores, these new results, published in the Journal of Hymenoptera Research, reveal that not only do the ants behave in ways to minimize damage to their hosts, but when damage does occur, they actively work to fix it, particularly when their brood is directly threatened.

“I was totally surprised by the results,” says William Wcislo. “And I was impressed by how they developed a simple way to test the idea that ants repair damage to their home.”

*Azteca* ant and *Cecropia* plant responses to wounds in the stems a a sealed hole after 24 hours, but not yet filled in to the stem surface (arrow) b a fully patched and filled-in hole after 24 hrs, oozing sap from the ant-sealed wound (arrow) c a natural plant scar surrounding a 6.4 mm hole that was fully sealed by the ants, approximately 5 months later d a hole in a plant without ants after 24 hrs, showing the green wall of the opposite side of the stem (arrow).

Sloths and silky anteaters often visit Cecropia trees and their sharp toenails sometimes pierce the wood, so the researchers speculate that these occurrences, which are far more common and ancient threats to the Cecropia than teenagers shooting clay balls at them, could have led Azteca alfari ants to evolve the observed repair behavior when their host plant is damaged.

Their experiment also left them with new questions, since not all of the ant colonies repaired the damage to their host plants. Understanding what factors influence the ants to take action could be the subject of future research for these budding scientists, although perhaps to be addressed after graduating from high school.

“Sometimes messing around with a slingshot has a good outcome,” said lead author Alex Wcislo. “This project allowed us to experience first-hand all the intricacies behind a scientific study. All in all, it was a great learning experience, especially considering the difficulties associated with fulfilling this due to COVID-19.”

Research article:

Wcislo A, Graham X, Stevens S, Toppe JE, Wcislo L, Wcislo WT (2021) Azteca ants repair damage to their Cecropia host plants. Journal of Hymenoptera Research 88: 61-70. https://doi.org/10.3897/jhr.88.75855

Vibes before it bites: 10 types of defensive behaviour for the False Coral Snake

The False Coral Snake (Oxyrhopus rhombifer) may be capable of recognising various threat levels and demonstrates ten different defensive behaviours, seven of which are registered for the first time for the species. Scientists from the Federal University of Viçosa (Brazil) published their laboratory observation results based on a juvenile specimen in the open-access journal Neotropical Biology and Conservation.

In a recent paper in the open-access journal Neotropical Biology and Conservation, a group of Brazilian scientists from the Federal University of Viçosa (Brazil) published ten different defensive behaviours for the False Coral Snake (Oxyrhopus rhombifer), seven of which are registered for the first time for the species. One of these is reported for the first time for Brazilian snakes.

Evolution shaped anti-predator mechanisms in preys, which can be displayed either with avoidance or defensive behaviours. The current knowledge about such mechanisms are still scarce for many snake species, but it is constantly increasing over the last years. These data are helpful for better understanding of the species ecology, biology and evolution.

The False Coral Snake (O. rhombifer) is a terrestrial snake species with a colouration like the true coral snake . The species has a wide geographic distribution, occurring in Argentina, Paraguay, Uruguay, Bolivia and all Brazilian biomes. Among its previously known anti-predator mechanisms, this species has already shown cloacal discharge, body flattening, struggling, erratic movements and hiding the head.

However, these behaviors were only a small part of what this species is capable of doing to defend itself! In November 2017, a juvenile male captured in the Atlantic Forest of southeastern Brazil was observed under laboratory settings, where the scientists would simulate a predation attempt with an increasing threat level.

We released the snake on to the laboratory bench and let it notice our presence. The animal remained motionless at first, then performed a pronounced dorsoventral flattening of the anterior part of the body, raised its tail, adopted an S-shaped posture, raised the first third of the body and performed brief body vibrations. Then we approached the snake, which remained with the same posture and body vibrations. When we touched the animal (not handling), it remained with the S-shaped posture, keeping the first third of the body elevated and the dorsoventral flattening (however, less accentuated) and started to display erratic movements, false strikes and locomotor escape. When handled, the snake only struggled,
shares the lead scientist Mr. Clodoaldo Lopes de Assis.

Amongst ten recorded behaviour types only three were among those already registered for this species. Since defensive responses in snakes decrease as body size increases, juveniles exhibit a broader set of defensive behaviour than adults. Because of that, some types of behaviour described in this study might be explained either by physical constraints or stage of development of the individual.

Some types of behaviour resemble the ones of true coral snakes of the genus Micrurus, a group of extremely venomous snakes. Thus, this similarity may be linked with the mimicry hypothesis between these two groups, where harmless false coral snakes take advantage of their similar appearance to the true coral snakes to defend themselves.

Another type of anti-predation mechanism shown — body vibrations — is yet an unknown behaviour for Brazilian snakes and has been recorded for the first time. This type of behaviour is difficult to interpret, but could represent a defensive signal against non-visually orientated predators.

Finally, defensive strategies of the specimen differed according to the threat level imposed: starting from discouraging behaviour up to false bites, erratic movements and locomotor escape.

Some defensive types of behaviour displayed by the juvenile *Oxyrhopus rhombifer*
Credit: Mr. Clodoaldo Lopes de Assis
License: CC-BY 4.0

O. rhombifer may be capable of recognising different threat levels imposed by predators and adjusting its defensive behaviour accordingly,
highlights Mr. Clodoaldo Lopes de Assis.

Through such simple laboratory observations we can get a sense of how Brazilian snakes are yet poorly known regarding their natural history, where even common species like the false coral snake O. rhombifer can surprise us!
Mr. Clodoaldo Lopes de Assis adds in conclusion.

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Original source:
Lopes de Assis C, José Magalhães Guedes J, Miriam Gomes de Jesus L, Neves Feio R (2020) New defensive behaviour of the false coral snake Oxyrhopus rhombifer Duméril, Bibron & Duméril, 1854 (Serpentes, Dipsadidae) in south-eastern Brazil. Neotropical Biology and Conservation 15(1): 71-76. https://doi.org/10.3897/neotropical.15.e48564

The first drywood termite known to use snapping stick-like mandibles to defend its colony

Tasked to defend the colony from attackers, the specialised soldier caste in some termite species has evolved various impressive mechanisms, including plug-like heads – meant to block intruding ants trying to invade their lairs, and mouthparts designed to bite and pierce.

Still, there are even more spectacular soldiers, such as a recently discovered drywood termite species, whose unique long and slender, stick-like snapping mandibles produce one of the highest acceleration speeds measured in a living organism. Rather than bite, these peculiar ‘jaws’ deliver powerful strikes at enemies bold enough to stand in the way of the soldier termite and its colony.

The scientists describe the new termite’s specialty in detail:

“Roisinitermes employs a unique strategy of snapping, achieved by long and slender mandibles pressed against each other in a defensive encounter. When this potential energy is released, the left mandible springs over the right and the resultant snap is forced onto the opponent if it is in the path of the strike.”

Discovered in Cameroon, this striking species is the first drywood termite found to rely on snapping mandibles as a defense strategy. Given that until now there had been a single subfamily (Termitinae) known to have developed such, the very existence of the new insect poses a whole new set of questions before scientists. Have snapping mandibles evolved independently in two evolutionary lineages? Or, is it that these groups share a distant kin relationship which has gone unnoticed for that long?

The new drywood termite, which is also assigned to a new genus, is named Roisinitermes ebogoensis, and is described in the open access journal ZooKeys by an international team of researchers, led by Dr Rudolf Scheffrahn of the Institute for Food and Agricultural Sciences at University of Florida, Davie, USA. Although this particular species is not thought to be a pest, some drywood termites cause serious damage to wooden structures around the world.

Both colonies studied by the scientists were found near the Ebogo II village, which also stands behind the name of the species. The first unusual colony to draw the attention of the scientists was collected from a forest on an island in the Nyong River, where it lived in a thin (3 cm) and long (over 3 m) broad-leaf tree branch suspended from a canopy. The second one – in a 15-mm thick dead liana branch hanging from a tree in a nearly pristine rainforest.

The team expects that future research will shed more light on the origins and evolution of the newly discovered termite.

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Original source:

Scheffrahn RH, Bourguignon T, Akama PD, Sillam-Dussès D, Šobotník J (2018) Roisinitermes ebogoensis gen. & sp. n., an outstanding drywood termite with snapping soldiers from Cameroon (Isoptera, Kalotermitidae). ZooKeys 787: 91-105. https://doi.org/10.3897/zookeys.787.28195

Towards untangling the ‘antennal grabbing’ phenomenon in mating cuckoo bees

Scientists report this behavior for the first time in the genus Nomada, following both lab and field observations in Germany

One can seldom spot a cuckoo bee, whose peculiar kleptoparasitic behaviour includes laying eggs in the nests of a certain host bee species, let alone a couple mating.

Nevertheless, German scientists – Dr. Matthias Schindler, University of Bonn, Michaela Hofmann and Dr. Susanne S. Renner of the University of Munich, and Dr. Dieter Wittmann, recently managed to record copulation in three different cuckoo bee species in the genus Nomada.

Intriguingly, in field and lab settings alike, the observed couples demonstrated the phenomenon the researchers called “antennal grabbing” where the male cuckoo bee winds his antennae around

*Insertion phase of copulation in a couple of the species Nomada flavoguttata. Note the male’s antennae spirally entangling the female’s.*

the female’s during copulation, thus transferring pheromones. Even though such behaviour is relatively common in Hymenoptera, this is the first known record for the genus Nomada.

While the particular biological reason for the “antennal grabbing” in different species remains unsettled, the scientists discuss the phenomenon in view of both previous hypotheses and their own observations in a new paper published in the open access Journal of Hymenoptera Research.

The courtship in Nomada cuckoo bee starts with the ‘swarming’ of males at willow shrubs and gooseberry or their patrolling in groups with males of the Andrena or Melitta species that will “foster” their offspring.

*Two males of the species Nomada flavoguttata patrolling at a blossom of a common dandelion.*

There is no aggression among the males. They were observed to rub their bellies and heads against the grass, in order to leave sexual pheromones, thus marking the “dating spot” for potential mates.

Earlier chemical studies of Nomada bees noted that the mandibular glands of males produce chemical compounds identical with those of their Andrena or Melitta hosts, leading to the suggestion that the males transfer pheromones that help the females mimic the odor of the host bee, and later enter its nest unnoticed to lay its eggs. An alternative explanation for the “antennal grabbing” is that males are spraying a substance onto the females to make them unattractive to other potential mates.

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Original source:

Schindler M, Hofmann MM, Wittmann D, Renner SS (2018) Courtship behaviour in the genus Nomada – antennal grabbing and possible transfer of male secretions. Journal of Hymenoptera Research 65: 47-59. https://doi.org/10.3897/jhr.65.24947

Scientists use forensic technology to genetically document infanticide in brown bears

Modern open-source software helped the researchers identify the male that killed a female and her two cubs

Scientists used a technology designed for the purposes of human forensics, to provide the first genetically documented case of infanticide in brown bears, following the murder of a female and her two cubs in Trentino, the Italian Alps, where a small re-introduced population has been genetically monitored for already 20 years.

The study, conducted and authored by Francesca Davoli, The Italian Institute for Environmental Protection and Research (ISPRA), Bologna, and her team, is published in the open access journal Nature Conservation.

To secure their own reproduction, males of some social mammalian species, such as lions and bears, exhibit infanticidal behaviour where they kill the offspring of their competitors, so that they can mate with the females which become fertile again soon after they lose their cubs. However, sometimes females are also killed while trying to protect their young, resulting in a survival threat to small populations and endangered species.

“In isolated populations with a small number of reproductive adults, sexually selected infanticide can negatively impact the long-term conservation of the species, especially in the case where the female is killed while protecting her cubs,” point out the researchers.

“Taking this into account, the genetic identification of the perpetrators could give concrete indications for the management of small populations, for example, placing radio-collars on infanticidal males to track them,” they add. “Nevertheless, genetic studies for identifying infanticidal males have received little attention.”

Thanks to a database containing the genotypes of all bears known to inhabit the study site and an open-source software used to analyse human forensic genetic profiles, the scientists were able to solve the case much like in a television crime series.

Upon finding the three corpses, the researchers were certain that the animals had not been killed by a human. In the beginning, the suspects were all male brown bears reported from the area in 2015.

Hoping to isolate the DNA of the perpetrator, the researchers collected three samples of hairs and swabbed the female’s wounds in search for saliva. Dealing with a relatively small population, the scientists expected that the animals would share a genotype to an extent, meaning they needed plenty of samples.

However, while the DNA retrieved from the saliva swabs did point to an adult male, at first glance it seemed that it belonged to the cubs’ father. Later, the scientists puzzled out that the attacker must have injured the cubs and the mother alternately, thus spreading blood containing the inherited genetic material from the father bear. Previous knowledge also excluded the father, since there are no known cases of male bears killing their offspring. In fact, they seem to distinguish their own younglings, even though they most likely recognise the mother.

To successfully determine the attacker, the scientists had to use the very small amount of genetic material from the saliva swabs they managed to collect and conduct a highly sophisticated analysis, in order to obtain four genetic profiles largely overlapping with each other. Then, they compared them against each of the males reported from the area that year. Eventually, they narrowed down the options to an individual listed as M7.

“The monitoring of litters is a fundamental tool for the management of bear populations: it has allowed the authors to genetically confirm the existence of cases of infanticide and in the future may facilitate the retrieval of information necessary to assess the impact of SSI on demographic trends,” conclude the researchers.

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Original source:

Davoli F, Cozzo M, Angeli F, Groff C, Randi E (2018) Infanticide in brown bear: a case-study in the Italian Alps – Genetic identification of perpetrator and implications in small populations. Nature Conservation 25: 55-75. https://doi.org/10.3897/natureconservation.25.23776

How bears bulk up ahead of the summer: A study into the Asiatic black bear’s spring diet

Much like gym enthusiasts, every year Asiatic black bears seem to be on the lookout for protein-rich food ahead of the summer, so that they can bulk up on lean muscle mass in place of the fat tissue formed last year prior to hibernation. This was concluded in a study by Dr. Shino Furusaka, Tokyo University of Agriculture and Technology and his team, based on direct observations on bears living across an area of about 60 km2 in Japan. The study is published in the open access journal ZooKeys.

In order to determine the bears’ food preferences and habits, the scientists followed a large number of animals in the Ashio area of the Ashio-Nikko Mountains in Japan from April to July in both 2013 and 2014. To avoid unnecessary intrusion, they stayed at a distance of at least 200 metres using video cameras with telescopic lenses to document the sightings. Having documented the plant species the bears consumed, the researchers studied their nutritional content and made conclusions about the nutrients needed for the species after hibernation.

While heavily dependent on food availability, generally the bears were noted to prefer food which is high in protein, but poor in fibre — likely because their stomachs and intestines were unable to efficiently digest the latter. Furthermore, the protein-rich diet ensures that the muscle mass is rebuilt to replace the lost winter fat.

Interestingly, the bears were observed to change their food preferences as spring progressed and that seemed to be linked to the shifts in the nutritional value of the available food.

Starting with their observations at the beginning of April, the scientists did not record any feeding behaviour until the end of the month. As leaf flush was yet to occur, the animals were active and feeding on overwintered grass. However, in early May, the bears began consuming newly emerged leaves, grass and, later in the month, they added flowers to their menu.

A shift in behaviour occurred in the following months. In June and July, the bears were seen to feed mainly on ants, with a small portion of their food intake consisting of grasses, sika deer carcasses and bees. Curiously, when the scientists looked into the nutritional content of the same plants which the animals sought only a few weeks ago, they found out that now they were significantly poorer in protein and richer in fibre.

Another finding showed that the calories in the different items were not related to the choice of food which likely proves that the key factor is none other than the amount of protein, provided that the fibre value is low enough for good digestibility.

Understanding the food preferences and habits of animals, as well as the reasons behind them, is essential for the development and revision of habitat management plans. However, previous knowledge of the feeding behaviour of Asiatic black bears has been based solely on faecal analyses which has not provided sufficient details on which nutritional factors influence the use of particular foods.

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Original source:

Furusaka S, Kozakai C, Nemoto Y, Umemura Y, Naganuma T, Yamazaki K, Koike S (2017) The selection by the Asiatic black bear (Ursus thibetanus) of spring plant food items according to their nutritional values. ZooKeys 672: 121-133. https://doi.org/10.3897/zookeys.672.10078

The bold and the shy one: Could woodlice have personalities?

Unlike larger animals and even other invertebrates, the theory for the presence of personality traits in terrestrial isopods had not been studied before the research conducted by Dr. Ivan Tuf’s team.

Known to react to an external impact with varying in its duration death feigning, or tonic immobility, several hundreds of Common rough woodlice were observed while responding to random sequences of touch, squeeze and drop. When compared, the results showed there is in fact a significant individual pattern of defensive behaviour. The study is published in the open-access journal ZooKeys.

In order to prove that the tested P. scaberwoodlice actually possess personalities, the scientists had to look for repetitiveness in their reactions to external impacts. Over the three-week observations, consisting of five experimental sets and four-day breaks, Dr. Tuf and his team recognised consistency in the reactions in the individuals. They even managed to identify some of them as “more ‘bold'” and others – “more ‘shy’.”

However, a number of other factors were found to influence the woodlice’ protective reactions such as habituation and body size. Ten minutes in a particular environment proved enough for a woodlouse to habituate it. As a result, their sensitivity towards the same stimuli decreased.

Similarly, it was not as noticeable with the larger specimens. Unlike their tinier relatives, they are capable of using chemical protection due to their better developed physiology. Nevertheless, the longest reaction time being measured in a medium-sized woodlice proves that body size is not of such importance.

Yet, it is still unclear whether the woodlice’ behaviour changes over time. If such a trend is present, then their reactions to the external stimuli is also likely to change.

“Investigation of long-time stability of behavioural traits in terrestrial isopods should be a possible goal of future studies,” the scientists suggest in conclusion.

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Original source:

Tuf IH, Drábková L, Šipoš J (2015) Personality affects defensive behaviour of Porcellio scaber(Isopoda, Oniscidea). In: Taiti S, Hornung E, Štrus J, Bouchon D (Eds) Trends in Terrestrial Isopod Biology. ZooKeys 515: 159-171. doi: 10.3897/zookeys.515.9429