For people that are familiar with cichlids the word aggression is certainly not strange in relation to these wonderful animals. It is probably one of the more characteristic aspects of them. Already one of the first cichlids kept in the aquarium: Rocio octofasciata (first introduced in Hamburg in 1904), got dubbed the “Jack Dempsey” after the famous American pugilist (William Harrison Dempsey, 1895-1983). They were labeled as mean. Of course, at the time, there was not much with which to compare its aggressiveness in terms of cichlid species kept in aquarium, and nowadays the English common name would seem rather exaggerated to any person familiar with cichlids.
Aggression is an important and necessary behavior for survival, which has strong evolutionary roots. Cichlids and other animals are aggressive and fight for a reason. However, fighting is avoided as much as possible. Aggression and fight may have a high cost for an animal and have to be used just in necessary cases, directed to specific creatures and in the minimum amount possible. The costs for aggression are many: the time involved in the fight, the energy expended, the distraction it causes from potential predators, the injuries that originate from fighting and their potentially resulting reduced fitness, and ultimately, death. Certainly, no animal would be willing to get involved in a fight if it weren’t absolutely necessary, as otherwise it goes against the survival of its lineage.
Aggression and fight are used to secure limited and necessary resources such as food, mates and protection of their descendants and in some cases relatives carrying the same genes. In each situation every organism makes a quick evaluation of what is to be won using aggression, assess its risks and would just engage in fighting when the possibilities of getting more benefits than losses are in its favor.
One of the reasons organisms use aggression is to secure a feeding territory with the necessary resources for its well-being, interestingly enough, this is not the main reason why cichlids get into fights. As Dr. George Barlow explains in his book "The Cichlid Fishes" most cichlids live under variable conditions that can provide a steady source of food without the need to establish a territory. Rivers have ever changing environments that make useless to establish a permanent territory, and so cichlids avoid aggressiveness related to this goal.
An exception is however present in several genera inhabiting the great lakes of Africa: Chindongo species inhabiting rocky reefs in Lake Malawi lack specializations that would allow them to obtain their food with little competition, and they trust instead the aggressive guarding of what are referred to as “algal gardens”; i.e., a piece of real state on sun exposed rocks where algae can grow for their consumption. The type species of Chindongo: C. bellicosus (bellicosus is aggressive in Latin) reflects in its name this characteristic behavior. In Chindongo species, not just males maintain territories, but also females and young adults. Chindongo species, as all other Lake Malawi cichlids, are maternal mouth-brooders. Females enter neighboring courting males’ territories to spawn with them, collect fertilized eggs in their mouth and quickly return to their algal garden, where they mouth-brood their eggs and wrigglers for three to four weeks before releasing them. They keep defending their territory even when, most of the time, mouth-brooding females can’t feed themselves.
In other cases, aggressive behavior is used to maintain territories for breeding purposes, although these territories in most cases are temporary. Cichlid males of mbuna (rock dwelling cichlids) of Lake Malawi establish territories to attract females to spawn. Males are normally very colorful and defend strongly their territories, while passing females are impressed by the color, displays, and territory and are lured to enter to get their eggs fertilized by the guardian of the real estate.
Some species elaborate on this behavior. One favorite example for me concerns ‘Lamprologus’ callipterus, a shell-brooding cichlid endemic to Lake Tanganyika. Although this shrimp eating cichlid schools in the hundreds throughout foraging areas when young, by the time they reach sexual maturity males establish shell-gardens of about 40 to 60 cm that are aggressively protected. Such shell gardens are built up with shells over time. The much smaller females (‘Lamprologus’ callipterus is a vertebrate with one of the highest ratio of size difference between males and females) remain in one of the shells where they spawn and offer shelter to fry. Logically the more shells in the male’s territory the more females he gets, so he fights viciously with other males for this resource, and often steals shells from other males’ territories, many times including a female. This aggressive mode of living wears down territorial males, who only last a short time holding a territory, but tops in efficiency for passing its genes.
When cichlid real estate breeding areas are limited and pairs are many, territories are small and lay one against the other; in these cases pairs mostly defend the borders against neighbors. Pairs look to expend as less energy as possible on aggression. They know that neighbors are minding their own business, and hence efforts are just directed at keeping them inside their own territories, for which often the more economical solution is intimidation.
Pairs of Thorichthys species distributed in the Usumacinta ichthylological province in Mexico, Belize, Guatemala and Honduras, among others, are masters of this behavior. Male and female Thorichthys (except for one species: T. callolepis) have an ocellated black blotch on each opercle. When a pair tries to intimidate a neighboring pair, the gular pouches are extended forwards and the opercular black blotches create the illusion of eyes on a much bigger head, this often does the trick intimidating potential contenders. Pairs often defend their territories together by presenting at neighboring pairs at the territory’s border. They perform a protocol where one pair advances with the extended gular pouches extended, propelled by their tail, making the neighbor pair to go backwards, at one point they get into the neighbors’ territory and that switches intentions, with the neighbors pushing back the invading pair. The dance continues over and over but rarely any damage is caused to any fish involved. Thorichthys are not robust cichlids and very rarely damage any other fish. Other species have convergently evolved a similar behavior, like Herichthys tamasopoensis in northeastern Mexico and on the other side of the world Etroplus maculatus in India and Sri Lanka.
Aggression is not directed randomly, that would waste too much energy and create too much risk. Often, the main targets of aggression are members of the same species, what is known as intraspecific aggression, which represent the most direct competition. However, other species that are seen as competitors are also targeted. Any other species is just ignored; it is much more efficient to live in peace and keep the resources for valuable chores.
Often, and unlike intuition, very large piscivore cichlids are very mild tempered, the reason being that they do not have to protect a territory to secure their food, since their food is found moving around. One example of this is the huge Petenia splendida found in the Usumacinta ichthylological province, which can grow to more than 40 cm in the wild. During breeding time they balance their lack of aggressiveness to use in the defense of their fry by producing several thousand babies.
Cichlids normally first assess the risks before entering into a fight; they face their potential contenders and erect all fins to look bigger. If one individual determines that he holds no chance of winning it normally would just flee away and live another day, but a series of factors may lead even a much smaller individual into a fight. For example, if a cichlid is defending a valuable territory or if it has already expended a lot of time and energy into the care of its fry it may face and even turn away a much larger contender, which may not be looking for more than some food and may lack the necessary motivation to enter into a fight.
Once a fight is decided between two cichlids it is however not immediately engaged in full, but by taking incremental steps with the specific aim to make the contender quit, expending the least energy and producing the least damage. Fighting is dangerous and damage made to eyes or fins may imperil even the winner, producing a Pyrrhic victory and making it suffer the consequences. When the sum of motivation and strength of the contenders match, the fight is inevitable and if no one quits it may escalate to the death of one of the participants.
The first step of a fight is known as tail-beating. In this phase the two contenders place each other side by side with the head of one individual close to the tail of the other, or the head by the head, at this point they start undulating their bodies pushing water to each other causing pressure waves which can be easily felt in their lateral lines, this is done in an attempt to show their strength and convince the opponent to quit the fight.
If none of the contenders withdraws, the second phase of fighting proceeds when both individuals place in a position to face each other, opening their mouths, then they may proceed to grab each other by the jaw in a step known as jaw-locking. Once grabbing each other by the jaws they twist and push adding sudden lateral pulls in order to create damage to the jaws of the opponent. This is a dangerous step, since if damage is caused to the jaw it may have severe consequences, as fish depend on their mouths to defend and gather food; a damaged jaw is bad news.
If at this point no contender retreats, they proceed to the third phase of fighting, which is known as carouselling: In this phase the contenders start to chase each other’s tail swimming in close circles and trying to bite the caudal peduncle or fins of the opponent, causing damage to their propelling and stabilizing system, another vulnerable area. Scales start flying each time one individual bites the other. This phase may last for a longer time, effectively damaging both fishes the longer it takes.
At this point they may start alternating between jaw-locking and carouselling. Having a place where to flee to, at one point one of the contenders decides to quit avoiding the risk of impairing damage or death.
Experiments show that in a fight between two cichlids of equal size and motivation, the larger of the two fishes (even for a small amount) would generally win; as it is stronger, has a bigger mouth, larger fins, and more energy reserves. But when a smaller cichlid has a strong motivation, it may be equally able to win a fight to a much larger, less motivated individual. In all fights I have witnessed in natural habitats, just a few times I have seen fighters engaging in carouselling, and if they do one of the two contenders quickly quits and flees; so rarely much damage is done.
In the latter case there is one advantage, space to go away. They can just swim away, and they do. Things get much worse when cichlids are found in an enclosed space. Under such circumstances they can’t run away and fights often end with the dead of one fish, even if one individual quits the fight in its initial stage, it has nowhere to go and the other individual would chase and bite him to death. Every cichlid aquarist with sufficient time keeping cichlids has experienced this situation. A good aquarist knows how to successfully control it.
If you would like to learn more about this topic, I would highly recommend chapter five “Oh yeah? Put up your fins!” of the wonderful book by George Barlow “The Cichlid Fishes: Nature’s grand experiment in evolution” (2000). Also, a great article by Ron Coleman on this topic present in this site
Special thanks to Ad Konings for reviewing this article and giving me valuable comments.
- Barlow, George W.. 2002. "The Cichlid Fishes (Nature's Grand Experiment in Evolution)". Perseus Publishing. pp. 352 pp. ISBN: 9780738203768 (crc03927) (riassunto)
© Copyright 2020 Juan Miguel Artigas Azas, all rights reserved
Artigas Azas, Juan Miguel. (maggio 15, 2020). "Aggression in cichlids". Cichlid Room Companion. URL consultato in data aprile 13, 2021, da: https://cichlidae.com/section.php?id=308&lang=it.