For people who know cichlids, the word “aggression” is certainly not unfamiliar in relation to these wonderful animals. In fact, it is probably one of their main characteristics. One of the first cichlids kept in the aquarium, Rocio octofasciata (originally introduced in Hamburg in 1904), was considered such a mean fish that it was dubbed the “Jack Dempsey” after the famous American boxer.
Of course, at the time, there was not much to compare the cichlid’s aggression to in terms of cichlid species kept in aquaria, and nowadays the common name would seem rather exaggerated to any person familiar with cichlids.
Aggression is an important and necessary behavior for survival, and it has strong evolutionary roots. Cichlids and other animals are aggressive and fight for a reason, as fighting is to be avoided as much as possible. Aggression and fighting may have a high cost for any animal, so it must be reserved for necessary cases and directed toward specific creatures. The costs of aggression are many: the time involved in the fight, the energy expended, the distraction it causes from potential predators, the injuries that originate from the fighting, the potential for reduced fitness from those injuries, and even death.
So certainly, no animal would be willing to get involved in a fight if it weren’t absolutely necessary, as it threatens the survival of its lineage. Instead, aggression and fighting are used to secure limited and necessary resources, such as food and mates, as well as to protect offspring and, in some cases, to protect relatives carrying the same genes. In each situation, every organism makes a quick evaluation of what is to be won using aggression, assesses the risks, and only engages in fighting when the possible benefits outweigh the potential losses.
One of the reasons organisms use aggression is to secure a feeding territory with the necessary resources for their well-being. But interestingly enough, this is not the main reason why cichlids get into scuffles. As Dr. George Barlow explained in his book The Cichlid Fishes: Nature’s Grand Experiment in Evolution (Perseus, 2000), most cichlids live under variable conditions that can provide a steady source of food without the need to establish a territory. Rivers are ever-changing environments that make establishing a permanent territory useless, so cichlids avoid conflicts related to feeding territories.
An exception is present, however, 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 instead aggressively guard what are referred to as “algal gardens,” pieces of real estate on sun-exposed rocks where algae can grow for their consumption. The type species of Chindongo, C. bellicosus (from “aggressive” in Latin) is a nod to this characteristic behavior.
In Chindongo species, it is not just the males that maintain territories, but also females and young adults. Chindongo species, like all other Lake Malawi cichlids, are maternal mouthbrooders. Females enter neighboring courting males’ territories to spawn with them, collect fertilized eggs in their mouths, and quickly return to their algal garden, where they mouthbrood their eggs and wrigglers for three to four weeks before releasing them. They keep defending their territory even when, most of the time, mouthbrooding females can’t feed themselves.
In other cases, aggressive behavior is used to maintain territories for cichlid breeding purposes, although these territories are usually temporary. Male mbuna (rock-dwelling cichlids) of Lake Malawi establish territories to attract females to spawn. Males are normally very colorful and strongly defend their territories, while passing females are impressed by their color, displays, and territory and are lured to enter to get their eggs fertilized by the guardians 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 these shrimp-eating cichlids school in the hundreds throughout foraging areas when young, by the time the males reach sexual maturity, they establish shell gardens of about 16 to 24 inches (40 to 60 cm) that they aggressively protect. These gardens are built up with shells over time.
The much smaller females—‘Lamprologus’ callipterus males and females have one of the greatest size differences—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, taking a brooding female with them. This aggressive mode of living wears down territorial males, who only last a short time holding a territory, but they are tops in efficiently passing on their genes.
When cichlid breeding areas are limited and pairs are many, territories are small and close together; in these cases, pairs mostly defend the borders against neighbors. Pairs look to expend the least amount of energy possible on cichlid aggression. They know that neighbors are minding their own business, so their efforts are better spent just keeping them inside their own territories, for which the most economical solution is often intimidation.
Threat Displays and Fighting
Pairs of Thorichthys species distributed in the Usumacinta ichthyological province in Mexico, Belize, Guatemala, and Honduras 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 forward and the opercular black blotches create the illusion of eyes on a much bigger head, which often does the trick of intimidating potential contenders.
Pairs often defend their territories by displaying to neighboring pairs at the territory’s border. They perform a protocol whereby one pair advances with the gular pouches extended, propelled by their tails, to make the neighbor pair go backward. At some point, they will encroach into the neighbors’ territory, forcing the neighbors to turn the tables and push back the invading pair.
The dance continues over and over, but it rarely causes any damage to the fish. Thorichthys are not robust cichlids and very rarely do any damage to 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, as that would waste too much energy and create too much risk. The main targets of cichlid aggression are members of the same species, in what is known as intraspecific aggression, which represents 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 save the resources for more valuable activities.
Often, counterintuitively, very large piscivore cichlids are very mild-tempered, because they do not have to protect a territory to secure their food. Their food is found moving around. One example of this is the huge Petenia splendida, found in the Usumacinta ichthyological province, which can grow to more than 16 inches (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 an individual determines that it has no chance of winning, it normally just flees the scene and lives 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 put 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 only be seeking a convenient meal and thereby lacks the do-or-die motivation of the smaller fish in the fight.
Once a fight is initiated between two cichlids, they do not immediately engage full-tilt, but rather take incremental steps with the specific aim of making the other contender quit, expending the least energy, and causing themselves the least damage. Again, fighting is dangerous, and damage done to eyes or fins may imperil even the winner. If the motivation and strength of the contenders are roughly equal and neither backs down, the fight is on, and if no one quits, it may escalate even to the point of death for one of the participants.
The first step of a fight is known as tail-beating. In this phase, the contenders engage with each other side-by-side, with the head of one close to the tail of the other, or one’s head by the other’s head, and they start undulating their bodies, pushing water toward each other in pressure waves that can be felt in their lateral lines. This is done in an attempt to show strength and convince the opponent to quit the fight.
If neither of the contenders withdraws, the second phase of fighting begins. The combatants face each other, opening their mouths, and then may engage in what is known as jaw-locking. Grabbing each other by the jaws, they twist and push, using sudden lateral pulls to create damage to the jaws of the opponent. This is dangerous, because damage caused to a fish’s jaw may have severe consequences in its future ability to defend itself and gather food. A damaged jaw is a very bad development for a fish.
If at this point neither contender retreats, they proceed to the third phase of fighting, which is known as carouseling. The contenders chase each other’s tails, swimming in close circles and trying to bite the opponent’s caudal peduncle or fins to damage their vulnerable propelling and stabilizing systems.
Scales fly each time one individual bites the other. This phase may last for a longer time, and the longer it goes on, the more damage that is done.
At this point they may start alternating between jaw-locking and carouseling. One of the contenders will eventually decide to quit to discontinue the risk of injury or death and return to its territory.
Living to Fight Another DayExperiments show that in a fight between two cichlids of equal size and motivation, the larger of the two fishes (even by a small margin) generally wins, as it is stronger and has a bigger mouth, larger fins, and greater energy reserves. But when a smaller cichlid has stronger motivation, it may be able to win a fight with a much larger but less motivated individual. Of all the fights I have witnessed in natural habitats, only a few times have I seen fighters engaging in carouseling, and when they did, one of the contenders quickly quit and fled. So rarely is much damage done.
In the wild there is one advantage that fish in an aquarium don’t have: nearly unlimited space to run away. They can just swim away, and they do. Things get much worse when cichlids find themselves in an enclosed space and can’t get away. Under such circumstances fights often end with the death of one fish. Even if one individual quits the fight in its initial stage, it has nowhere to go, and the other individual may chase and bite him to death.
Every aquarist with sufficient experience keeping cichlids has seen this situation play out. A good aquarist knows how to successfully manage cichlid aggression in close quarters.
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