Category Archives: Behavior

Cat-handedness: can cats be left- or right-handed?

by Piter Kehoma Boll

In humans, as you may know, there is usually a preference for using one side of the body to perform a task, a thing called laterality. And we have a strong tendency to be right-handed, with about 90% of humans using their right side to perform most unilateral tasks. Several studies revealed that many other animals, at least among vertebrates, display laterality as well.

A recent study investigated laterality in the domestic cat during spontaneous behaviors in contrast with the more common experiments using forced behaviors, such as making the cat try to reach food. They looked for a side preference in cats during the behaviors of lying side, stepping down and stepping over.


Photo by Juan Eduardo de Cristófaro.*

The result indicated that about one third of the cats is left-pawed, one third is right-pawed and one third is ambidextrous while moving up and down, but there is no clear preference for lying on their right or left side. Thus, we can see that, differently from humans, there is no strong bias to use one side of the body in cats, at least not when looking at cats in general.

When we consider sex, though, there was a significant difference: male cats tend to be left-pawed, while female cats are usually right-pawed. That would be very useful if cats danced the waltz.

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McDowell, L. J.; Wells, D. L.; Hepper, P. G. (2018) Lateralization of spontaneous behaviours in the domestic cat, Felis silvestris. Animal Behavior135: 37–43.

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The natural-unnatural fallacy: let’s stop with this bullshit

by Piter Kehoma Boll

This post may upset some people, perhaps people from very different backgrounds and very different points of view regarding society or human practices, but I feel that I have to discuss this subject that has been used as a way to justify or condemn some behaviors.

Everybody has already heard, and perhaps even uses, the argument of “this is not natural” as a justification to oppose something. You can hear homophobes use it to condemn homosexuality, vegans to condemn the ingestion of meat, or even old people to lament the death of a child. It is sometimes called “argumentum ad naturam” or “appeal to nature”, a fallacy that considers that something natural is always better than something unnatural.

When a homophobe says that he or she is against homosexuality because it is not natural, their oppositors, people who defend the freedom of sexuality, quickly present them with evidences of homosexuality in other species. I myself, being a gay man, used, in the past, examples of other gay animals to explain that homosexuality is indeed natural.


Oh, yeah, babe. Two male lions having sex. Photo by Wikimedia user Rufus46.*

Regarding human diet, we can find the same thing, including two opposite groups using this very same argument. You can see vegetarians advocating against the consumption of meat because of our dentition or intestine, which are not typical of a carnivorous species. On the other hand, people who defend the so-called “paleo” diet try to reconstruct a diet that was common to our pre-historical ancestors, which would be our “natural” diet, and thus they consume large amounts of meat and fruits and avoid consuming grains, large amounts of sugar or other food that need to be domesticated. In the same way, other people, such as vegans (and even paleo lovers) are against consuming milk because this is a baby food and should not be ingested by adult mammals, afterall “it is not natural” to take the milk of a female of another species and drink it.


Several ant species “milk” aphids to drink the sweet secretions (honeydew) that they release. Photo by Friedrich Böhringer.**

Now let me tell you something: this all means shit. This is not how things work in the real world, which by the way is the same as nature. When we use the argument of something being natural or unnatural, we are implying that there is a pre-established way for things to work, that there is a purpose in life. Well, there is not! Do you know natural selection, right? Well, it basically states that the most successful variations of something are the ones that will survive, regardless of what they are or how they are used. The mouth evolved primarily as an opening through which animals ingest food, but we use our mouths to many different things, such as to speak, breathe, kiss, hold things, or give blowjobs. Are those things unnatural? Who cares? As long as the mouth is good at doing it, it will continue to be used to do it.

And more than that, using other species as a comparison to things that are natural or not for humans is ridiculous. Just because we are the only species that write, is writing unnatural? If we consider that to be true, then we can apply it to find unnatural behaviors in any other species. As long as a behavior is only found in a single species, it would be unnatural.


The satin bowerbird is the only species that uses blue objects to decorate its bower in order to attract a female. Is its behavior unnatural because of that? Photo by Joseph C Boone.***

As a social and (supposedly) scientific species, we should consider a behavior as good or bad based on its consequences to society or to individuals, as well as to the world as a whole. Murdering is bad not because it is unnatural, but because it kills people! Pollution is not bad because it is unnatural, it is bad because it pollutes! So more than only being stupid because of its assumption that natural things are good and unnatural things are not, the appeal to nature is also stupid because there is no way to separate things in natural and unnatural. Let’s grow up intellectually and stop using this bullshit of an argument at all.

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The bat folk songs: cultural evolution in our winged relatives

by Piter Kehoma Boll

For a long time, culture was considered a human trait, but nowadays we recognize the existence of culture in many other species, such as other primates, whales and some birds too. Now there are some evidences of culture being found in bats too.

A group of researchers from China studied the calls of the Chinese rufous horseshoe bat (Rhinolophus sinicus) across different populations and compared them to genetic and environmental variables to determine whether the differences where linked to genetic differences between the populations or to different environments that would force the bats to change their calls in order to use them more successfully.


The smile of a cult bat (Rhinolophus sinicus). Photo by Ecohealth Alliance, extracted from Eureka Alert.

The results indicate that none of those two factors were strongly linked to the acoustic differences in the calls. The most likely explanation is that the differences happen due to cultural drift. The bats are teaching a way to speak to their children that is slightly different from what their neighbors speak, even if the neighbors are genetically similar and live in a similar environment.

As an animal’s call is an important variable during mating, this may eventually lead to reproductive isolation even without genetic differences. Culture can also shape evolution!

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Xie, L.; Sun, K.; Jiang, T.; Liu, S.; Lu, G.; Jin, L.; Feng, J. (2017) The effects of cultural drift on geographic variation in echolocation calls of the Chinese rufous horseshoe bat (Rhinolophus sinicus)Ethology 123(8): 532-541.

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Badass females are unpopular among praying mantids

by Piter Kehoma Boll

One of the most iconic representations of praying mantids is that of a female eating the male after (or during) sex, an unpleasant scenario that starts with a beheading before the poor male even finishes his job.


Delicious male meal. Photo by Wikimedia user Classiccardinal.*

According to some studies, when the male is beheaded, he increases the pumping of semen into the female, thus increasing the chances of fecundation. This could make one think that being eaten is actually an advantage to the male, as it makes him have more offspring.

Several observations with different species show the opposite though. Males make everything they can to avoid being eaten by the female, as it allows them to copulate with additional females. But how can they escape from such a gruesome destiny?

It is known that hungry females are more eager to eat the partner than satiated ones. Well-fed females (fat ones) are also less likely to have a meal in bed than malnourished ones. Males can tell whether a female is hungry or malnourished and thus avoid those in such conditions. They like fat and fed females. But this is not the only thing that males take into account when choosing the appropriate mother for their children.

A study from 2015 by researchers of the University of Buenos Aires have shown that males of the species Parastagmatoptera tessellata, found in South America, also choose females based on their personality.

In a laboratory experiment, a male was put in a container where he could see two females, one aggressive and one non-aggressive. Another male was presented to both females (which were unable to see each other) and the aggressive female always attacked the male, while the non-aggressive one never did. After watching how each female behaved, the male received access to both and could choose his favorite one.

And guess what? The non-aggressive one was chosen most of the time. This means that males are not only able to tell whether they are likely to be eaten based on the female’s hunger and nutritional condition, but also by analyzing the behavior of the female towards other males.

See also:

Gender conflict: Who’s the man in the relationship?

Male dragonflies are not as violent as thought

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Lelito, J., & Brown, W. (2008). Mate attraction by females in a sexually cannibalistic praying mantis Behavioral Ecology and Sociobiology, 63 (2), 313-320 DOI: 10.1007/s00265-008-0663-8

Scardamaglia, R., Fosacheca, S., & Pompilio, L. (2015). Sexual conflict in a sexually cannibalistic praying mantid: males prefer low-risk over high-risk females Animal Behaviour, 99, 9-14 DOI: 10.1016/j.anbehav.2014.10.013

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Don’t let the web bugs bite

by Piter Kehoma Boll

If you think spiders are scary creatures, today you will learn that they are scared too. But what could scary a spider? Well, a web bug!

We usually think of spider webs as an astonishing evolutionary achievement of this group of arachnids and a very efficient way to capture prey without having to pursue them. Webs are sticky, resistant, and only spiders themselves can move freely through them. The only problem is that this is not true.


A thread-legged assassin bug (Emesaya sp.) feeding on a spider after invading the spider’s web in the Western Ghats, India. Photo by Vipin Baliga.*

A group of bugs that conquered the spider world are the so-called thread-legged assassin bugs, which comprise the subfamily Emesinae of the assassin bugs (family Reduviidae). As the name implies, the assassin bugs are a group of true bugs (suborder Heteroptera) that are expert killers of other creatures.

During their evolution, the thread-legged assassin bugs seem to have acquired a special taste for spiders and throughout the world they are usually associated with this eight-legged predators. In many cases, such as the one seen in the picture above, the bugs prey on the spiders, having developed the ability to move through the webs. They usually produce vibrations on the web that attract the spiders. Those, thinking that they caught a prey, are lured directly to their death in the legs and proboscis of the terrible bug.

Some thread-legged assassin bugs have, however, found another way to harass spiders: by stealing their food. In the latter scenario, the bugs usually wait close to or on the spider’s web and, when an insect is caught, they steal it from the spider by ripping it off the web. This kind of behavior is called kleptoparasitism, which means “parasitism by stealing”.

But how can spiders avoid this bug nightmare?

Until recently, it was thought that spiders were safe inside caves. Although emesinid bugs do occurr in caves, their association with spiders seemed to be weaker or non-existent there. But new findings are revealing that they pursue our arachnid fellows even to the deepest abysses of Earth.

The earliest cave-dwelling thread-legged assassin bug known to prey on spiders is Bagauda cavernicola, from India. Its spider-eating habits are known since the first decades of the 20th century.

The second species, Phasmatocoris labyrinthicus, was found almost a century later, in 2013, in Arizona, USA. More than only preying on spiders, such as the species Eidmanella pallida that lives in the same cave, P. labyrinthicus seem to have developed the ability to manipulate abandoned spiderwebs and use them to detect and capture prey for their own consumption. Only a single instance of such a behavior has been recorded and the species’s behavior needs further studies.


Phasmatocoris labyrinthicus feeding on the spider Eidmanella pallida in the Kartchner Caverns, Arizona, USA. Photo extracted from Bape, 2013.

Now, only 3 years later, there are new evidences of more thread-legged assassin bugs molesting spiders in caves. And this time the observations were made in Minas Gerais, Brazil. One individual of the bug species Emesa mourei was seen standing on the web of a recluse spider (Loxosceles similis) while the spider was at the web’s edge. Another specimen of E. mourei was seen feeding on a fly near the web of a pholcid (cellar spider). The fly and the legs of the bug had vestiges of silk, indicating that the bug stole the fly from the spider. Another bug species, Phasmatocoris sp., was observed on a web of the cellar spider Mesabolivar aff. tandilicus. If this species of Phasmatocoris manipulates spider webs the same way that P. labyrinthicus seems to do is something yet to be investigated.


Nymph of Emesa mourei feeding on a fly that it apparently stole from a pholcid spider in the cave Lapa Arco da Lapa, Minas Gerais, Brazil. Photo by Leonardo P. A. Resende, extracted from Resende et al., 2016.

With three different and very distant records of thread-legged assassin bugs associated with spiders in caves, it is clear that the poor arachnids cannot get rid of those bugs even if they run down into the bowels of the Earth.

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PAPE, R. (2013). Description and Ecology of A New Cavernicolous, Arachnophilous Thread-legged Bug (Hemiptera: Reduviidae: Emesini) from Kartchner Caverns, Cochise County, Arizona Zootaxa, 3670 (2) DOI: 10.11646/zootaxa.3670.2.2

Resende, L., Zepon, T., Bichuette, M., Pape, R., & Gil-Santana, H. (2016). Associations between Emesinae heteropterans and spiders in limestone caves of Minas Gerais, southeastern Brazil Neotropical Biology and Conservation, 11 (3) DOI: 10.4013/nbc.2016.113.01

Wignall, A., & Taylor, P. (2010). Predatory behaviour of an araneophagic assassin bug Journal of Ethology, 28 (3), 437-445 DOI: 10.1007/s10164-009-0202-8

Wygodzinsky, P. W. 1966. A monograph of the Emesinae (Reduviidae, Hemiptera). Bulletin of the American Museum of Natural History, 133:1-614.

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Friday Fellow: Persian Carpet Flatworm

ResearchBlogging.orgby Piter Kehoma Boll

A flatworm again, at last! Not a land planarian, but a flatworm nonetheless.

If there is a group of flatworms that may put land planarians in second plan regarding beauty, those are the polyclads. Living in the sea, especially in coral reefs, polyclads are colorful and curly and may be mistaken by sea slugs.

The species I’m introducing here today is Pseudobiceros bedfordi, commonly known as the Persian carpet flatworm or Bedford’s flatworm. It is about 8 cm long and lives in coral reefs along Australia, Indonesia, Philippines and adjacent areas. See how beautiful it is:

A flatworm (Pseudobiceros bedfordi). Raging Horn, Osprey Reef, Coral Sea

The Persian carpet flatworm with its beautiful colors. Photo by Richard Ling.*

The colorful pattern of this and many other polyclad species is likely a warning about their toxicity, although there are few studies regarding toxicity in these animals. Being active predators, polyclads may use their toxins as a way to subdue prey as well.

But the most interesting thing regarding the Persian carpet flatworm is its sexual behavior. As with most flatworms, they are hermaphrodites, so when two individuals meet and decide to have sex, they have to choose whether they want to play the male or the female role (or both). Unfortunately, most individuals prefer to be males, so those encounters usually end up in a violent fight in which both animals attack the partner with a double penis, a behavior known as penis fencing.


Two Persian carpet flatworms about to engage in penis fencing. Photo from Whitfield (2004), courtesy of Nico Michiels.**

At the end, the winner spurts its sperm onto the partner and leaves. The horrible part is yet to come, though. The sperm appears to be able to burn like acid through the receiver’s skin tissue in order to reach the inner tissues and thus swim towards the eggs. In some extreme cases the sperm load may be high enough to tore the receiver into pieces! If that’s not a good definition of wild sex, I don’t know what is.

See also: Gender Conflict: Who’s the man in the relationship?

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Whitfield, J. (2004). Everything You Always Wanted to Know about Sexes PLoS Biology, 2 (6) DOI: 10.1371/journal.pbio.0020183

Wikipedia. Pseudoceros bedfordi. Available at: <;. Access on November 24, 2016.

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What is behavior? Baby don’t ask me, don’t ask me, no more

ResearchBlogging.orgby Piter Kehoma Boll

One of the most difficult concepts to explain in biology is certainly life itself. But I am not here today to talk about the definition of life, but rather of another puzzling concept: behavior.

Behavior is the central subject of ethology and psychology, but it is also something more commonly understood by personal intuition, just like life, but no formal and widely accepted definition exists.

The simplest definition would be that behavior is something that is done. But in that case we fall into another difficult concept, the concept of “doing”, because what exactly is doing something?


Nobody doubts that a spider building a web is a behavior. Photo by Hedwig Storch.*

Some definitions of behavior that have been published are the following:

  • Tinbergen (1955): “The total movements made by the intact animal”. According to this definition, only animals can behave, so an unicellular alga swimming towards light, or a plant closing its leaves after being touched cannot be considered behaviors. On the other hand, the fact that an animal is orbiting the Sun because it is on Earth could be a behavior.
  • Beck et al. (1991): “External visible activity of an animal, in which a coordinated pattern of sensory, motor and associated neural activity responds to changing external or internal conditions”. Here again only animals would behave and only animals with some sort of nervous system. A behavior needs to include a response to a changing condition, i.e., a stimulus.
  • Starr & Taggart (1992): “A response to external and internal stimuli, following integration of sensory, neural, endocrine and effector components. Behavior has a genetic basis, hence is subject to natural selection, and it commonly can be modified through experience.” This definition does not use the word “animal”, but includes the need for neural components, which is almost the same thing.
  • Wallace et al. (1991): “Observable activity of an organism; anything an organism does that involves action and/or response to stimulation”. A more simple and broad explanation that encompasses many things that the previous definitions would exclude, but still includes at least the criterion that it is a response to stimuli.
  • Raven & Johnson (1898): “Behavior can be defined as the way an organism respond to stimulation”. A definition similar to the previous one.
  • Davis (1966): “What an animal does”. Very ambiguous and contradictory, as the same book includes a section on behavior of plants.
  • Grier & Burk (1992): “All observable or otherwise measurable muscular and secretory responses (or lack thereof in some cases) and related phenomena such as changes in blood flow and surface pigments in response to changes in an animal’s internal and external environment.” Another confuse, long, complex and ambiguous definition.

When a venus flycatcher closes its leaf to capture a fly, is it behaving? Photo by Stefano Zucchinali.*

Trying to find a way to create a unified definition of what is behavior, a group of researchers from the University of California, Berkeley, made a survey, published in 2009, in which they presented two lists to several biologists. The first contained a series of statements regarding behavior and the respondents should agree or disagree with the statement based on their assumption of what is behavior. The 13 statements were:

(A) ‘A developmental change is usually not a behavior.’
   (B) ‘Behavior is always a response to the external environment.’
(C)’A behavior is always an action, rather than a lack of action.’
(D) ‘All behaviors are directly observable, recordable and measurable.’
   (E) ‘People can all tell what is and isn’t behavior, just by looking at it.’
   (F) ‘Behavior is always influenced by the internal processes of the individual.’
   (G) ‘Behavior always involves movement.’
   (H) ‘Behaviors are always the actions of individuals, not groups.’
   (I) ‘Behavior is something whole individuals do, not organs or parts that make up an individual.’
   (J) ‘A behavior is always in response to a stimulus or set of stimuli, but the stimulus can be either internal or external.’
   (K) ‘Behavior is something only animals (including people) do, but not other organisms.’
   (L) ‘In humans, anything that is not under conscious control is not behavior.’
   (M) ‘Behavior is always executed through muscular activity.’


An arctic fox changing its fur color between seasons is a behavior or not? Photo by Wikimedia user Longdistancer.*

The second list included a set of 20 phenomena and the respondents should say whether they considered each phenomenon as representing a behavior or not. (In parentheses are the above statements under which the phenomenon would not be considered a behavior).

  1. Ants that are physiologically capable of laying eggs do not do so because they are not queens. (C, G).
  2. A sponge pumps water to gather food (B, M).
  3. A spider builds a web.
  4. A rabbit grows  thicker fur in the winter (A, G, I, M).
  5. A plant’s stomata (respiration pores) close to conserve water (I, K, M) .
  6. A plant bends its leaves towards a light source (K, M).
  7. A person’s heart beats harder after a nightmare (B, I, L).
  8. A person sweats in response to hot air (G, I, L, M).
  9. A beetle is swept away by a strong current (F, M).
  10. A rat has a dislike for salty food (B, C, G, J, M).
  11. A person decides not to do anything tomorrow if it rains (B, C, G, J, M).
  12. A horse becomes arthritic with age (A, B, E, G, M).
  13. A mouse floats in zero gravity in outer space (E, F, G, M).
  14. A group of unicellular algae swim towards water with a higher concentration of nutrients (F, H, K, M).
  15. A frog orbits the Sun along with the rest of the Earth (F, M).
  16. Flocks of geese fly in V formations (H).
  17. A dog salivates in anticipation of feeding time (B, G, I, M).
  18. Herds of zebras break up during the breeding season and reform afterwards (H).
  19. A chameleon changes color in response to sunlight (G, M).
  20. A cat produces insulin because of excess sugar in her blood (B, G, I, M).

Only four statements (A, F, I, J) were generally agreed, while seven (B, C, E, G, H, L, M) had general disapproval and two (D, K) were neither strongly approved nor strongly disapproved.

Considering the phenomena, seven (2, 3, 11, 14, 16, 17, 18) met the criterion for approval as behaviors based on the results of the statements and seven (4, 8, 9, 12, 13, 15, 20) met the criterion for rejection. The remaining six phenomena (1, 5, 6, 7, 10, 19) had major divergences as to whether they were behaviors.

Several respondents contradicted themselves. For example, many of them agreed that only animals can behave (statement K) but also considered that algae swimming towards water with higher concentration of nutrients is a behavior (phenomenon 14).


Most people would not consider that dandelion fruits carried by the wind are behaving.

Despite the high rate of disagreement, the group decided to propose a definition of behavior. And it is:

“Behavior is the  internally coordinated responses (actions or inactions) of whole living organisms (individuals or groups) to internal and/or external stimuli, excluding responses more easily understood as developmental changes.” (Levitis et al., 2009)

The question is not settled, though, and probably never will. Later, Dr. Raymond M. Berger, discussing the same subject, tells us that under the view of Descriptive Psychology, a behavior always includes eight parameters in the following formulation:

<B> = <I, W, K, K-H, P, A, PC, S>, in which:

B = behavior (e.g., Mary playing her queen of hearts in the contexts of a game of bridge).
I = identity of the person whose behavior it is (e.g., Mary)
W = want, the thing the person is attempting to achieve (e.g, to win a trick in the bridge game).
K = know, the cognitive parameter, the knowledge of how things work (e.g., queen vs. king, hearts vs. diamonds).
K-H = know-how, the ability to do what is being done (e.g., the ability to understand the rules of bridge, or the ability to move physical objects).
P = performance, the bodily processes involved in the behavior (e.g., Mary grasping and laying down her queen).
A = achievement, the outcome of the behavior (e.g., Mary takes the trick).
PC = personal characteristics, the indivudual’s difference parameter (e.g., Mary’s deep knowledge of strategy).
S = significance, what the behavior mean (e.g., Mary is playing bridge).


Playing a cardgame is certainly a behavior. A very complex one.

Such a “definition” is, in my opinion, too complex for most circumstances of animal behavior. However, I’m not completely happy with the definition by Levitis et al. either. I think it is hard to tell the difference between a response given by the whole organism vs. one of its parts. For example, when I cough because water entered my trachea, is my whole organism responding or only part of it? Would that be a behavior?

Also, I’m not sure whether we should really consider developmental changes as something different from other responses. If I had to define behavior, I most likely would say it is:

“An activity performed by an organism that is a response to a stimulus and is dependent on the organism’s internal processes”.


Why should a pupil changing size according to the environmental light not be considered a behavior?

And you? What do you think is behavior?

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Bergner, R. (2011). What is behavior? And so what? New Ideas in Psychology, 29 (2), 147-155 DOI: 10.1016/j.newideapsych.2010.08.001

Bergner, R. (2016). What is behavior? And why is it not reducible to biological states of affairs? Journal of Theoretical and Philosophical Psychology, 36 (1), 41-55 DOI: 10.1037/teo0000026

Levitis, D., Lidicker, W., & Freund, G. (2009). Behavioural biologists do not agree on what constitutes behaviour Animal Behaviour, 78 (1), 103-110 DOI: 10.1016/j.anbehav.2009.03.018

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