In the animal kingdom, those with more prominent appendages usually scare their enemies and win the fight even before it starts. The ones with smaller weapons tend to back off to a safe distance and run for their life. Although they may never know that the fear-inducing sword was only a plastic toy.
A new study led by Jason Dinh, aPh.D. in biology candidate from Duke University, shows that animal weapons can be similar to plastic swords that look impressive but are ultimately cheap.
Muscles, Appendages, Locomotions of Arthropods
Exoskeletons of arthropods are divided into plates to cover their body and appendages. It is somewhat analogous to the armor encasing a medieval knight.
According to Britannica, most arthropods move using their segetal appendages and their exoskeletons and muscles attached to the inside of their skeleton to act as a lever system. The exoskeletons provide a large surface area for attachment of the muscles, support, movement, and protection.
Some arthropods develop giant exoskeletons to support a large bulk because the new soft tissue might collapse following a molt.
Large, Chunky Animal Weapons Are Costly to Maintain
Antlers, tusks, and claws are examples of animal weapons that are often large, chunky, and heavy. However, they are metabolically costly to maintain. According to the University of Florida News, wild animals spend 30% to 40% of their total energy budget while at rest.
When scientists calculated the cost of maintaining the large hind legs of lead-footed bugs, they found that males invest more in their weapons while large males expend relatively less energy compared to smaller ones. Scientists discovered that the resting metabolic rate of one-legged bugs is down by almost a quarter in males while only about 7.9% in females.
Meanwhile, the largest deer develop large antlers compared to smaller deer, similar to how large elephants develop larger tasks than the smaller ones. Scientists said that the metabolic costs in maintaining their weapons are essential in shaping the evolution of diverse structures.
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Inert Components Helps Animals Cheat
In the new study published in Biology Letters, researchers showed that cheating helps animals survive. They found that the main component of a crab's shell is mostly inert and costs them nothing to maintain. It is similar to the keratin in rhino horns, bird feathers, and even in fingernails.
According to Phys.org, researchers investigated if animals could minimize the cost of maintenance of their weapons by using cheap tissues like chitin. They found that the larger the weapon, the larger the exoskeleton, which means the muscles do not grow proportionally leaving larger and cheap weapons.
Dinh said that these animals with large weapons are pretty good at deceiving their opponents who have trouble assessing whether they are stronger, bigger or just a prop to scare them. He added that fiddler crabs with bigger claws have more advantage in direct combat compared to other smaller crabs. Likewise, larger claws in snapping shrimps give them an edge to win a fight.
This also applies to bigger animals, such as chameleons, deers, and elephants, whose weapons are made of inert materials. At the end of the day, these weapons are honest indicators of how well they fight because animals use them to deceive others into how strong they are during the battle.
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