This is the last of our videos describing the harms that animals living in the wild face. It describes the many ways they can be harmed through accidents. Birds can collide with trees, elephants can get stuck in swamps, deers can puncture their eyes on low hanging branches, and squirrels can fall out of trees. Unlike humans, nonhuman animals have extremely limited ability to care for their injuries; often they are unable to take the time to heal because of the pressure to find food. Injuries can potentially become chronic or lead to death.
Also available as a chapter of our companion ebook to the video course Introduction to wild animal suffering: A guide to the issues
In previous sections we have seen how animals can be injured by external factors like certain weather events or by conflicts with other animals. Another way in which animals can be injured is due to accidents. These kinds of physical injuries are one of the most common threats to animals living in the wild. In some cases, animals incur severe injuries that kill them directly. In other cases, their injuries can affect them in ways that are indirectly fatal, for example, by reducing their ability to find food or to evade predators. Even when animals aren’t killed by their injuries, they can be left with chronic pain, especially when their injuries don’t heal properly.
Broadly speaking, we can categorize causes of injury into three main groups: conflict with other animals, injuries caused by severe weather and natural disasters, and accidents. Here, we’ll discuss how animals can be injured in accidents.
Animals living in the wild are subject to injuries in their everyday lives. Many accidents result from falls, collapsed dens or burrows, collisions, or getting stuck. Birds crash into trees, elephants get stuck in swamps, deers puncture their eyes on low-hanging branches, and squirrels fall out of trees. Invertebrates get appendages stuck and lose body parts in molting mishaps.
Many animals sustain crushing injuries caused by accidental trauma. For example, rocks or tree branches can fall on an animal. Some animals step on smaller animals. Male penguins can accidentally crush a chick while they are displaying, which can cause internal injuries. The type and degree of crushing injury depends on the amount of force, resulting in a range of injuries from minor bruising to severe hemorrhage, fractures, and rupture of internal organs.1
Vertebrates can suffer from a variety of fractures to bones in the spine, head and neck, limbs, jaw, wings, shell, or horns. Bone fractures in spine, limbs, and wings are common and can be fatal.2 Birds and squirrels sometimes fall from trees and break their legs or backs. Animals can also be injured while trying to traverse difficult terrain. A deer can break a leg if she slips on wet rocks while trying to make her way down to a river to drink. Horns are also made of bone and can bleed. If torn away near their base, skin will be torn as well.3
Walruses have been documented falling from cliffs, often in large numbers. It isn’t entirely clear what is responsible for these accidents. Walruses often haul out onto land to rest, and sometimes when the beaches are too crowded, they will climb up gentle slopes with cliffs on the other side. Once there, they can be frightened by polar bears, or they can simply lose their footing when returning to the sea.4
Tortoises and turtles can get fractured shells from falls, object impacts, or being trampled on by other animals. Large fractures can be quite serious. A turtle’s shell serves as a sort of backbone, and a turtle can be paralyzed or their lungs can collapse depending on where the crack is. If the fracture is deep, there can be blood loss. There are nerve endings in and around the shell, so it can be painful in the way any broken bone can cause pain. Some breaks can’t heal, and the ones that do, heal slowly. Because of their slow metabolisms, it can take years for a broken shell to heal. Shell rot can set in due to a fungal or bacterial infection under the crack. Aquatic animals are particularly susceptible to shell rot.
Birds have legs that are easily broken because they are small and often hollow. They may also be fragile due to malnutrition or excessive egg laying. Common causes of broken legs are falls, fights, accidental collisions with other animals, or being accidentally stepped on by a larger animal. The thinness of flying birds’ bones helps them in flight, but makes their bones more prone to shatter or fragment.5
Beaks can break from collisions or fights. A bird can also break her beak if she gets it stuck in something. If she panics and rips herself free, she can break her beak off. Beaks are made of skin covered in keratin (the same material as our fingernails). A beak is attached to bones, and the beak tip has a concentration of nerves and blood vessels. Birds use their beaks not only as mouths but also in the way we use our hands to pick things up. If a bird’s beak is injured, she may be unable to eat, drink, build a nest, or protect herself. Certain breaks cause bleeding, and in some cases, a bird can bleed to death from a broken beak. Injured beaks can also lead to breathing or sinus problems. Beaks don’t repair themselves, but the injured part can grow out. The tip continually grows because it is constantly wearing out due to use, but injuries far from the tip can be permanently disfiguring. An injured bird might only be able to eat soft food, which could make it difficult to survive in the wild.6
Bat and insect wings can tear from collisions with objects, plants, thorns, or from fungal infections. Tears in bat wings are serious injuries and can lead to blood loss.7 Tears can heal on their own, but torn wings affect flight capability, sometimes preventing flying altogether. The animals also require rest and extra energy to heal, and while they are healing, they are more vulnerable to starvation and other threats.
Animals in nature can sustain eye injuries due to foreign objects, punctures, or smoke. A common way an animal receives an eye injury is from running into branches. Because many animals escape predators and other threats by running into the woods, many run into low-hanging branches. While this usually only affects one eye, any permanent damage or vision loss can make the animal more prone to other harms in the future. Flying animals are at an advantage because there are fewer things to run into. However, birds can injure their eyes falling out of trees at an early age, or by running into branches when taking off. They can also be injured by talons in fights with other birds. Eye injuries that don’t heal inhibit a bird’s ability to fly.
Eyelid injuries, such as rips or punctures, often happen due to falls or running into something. The eyelid is a fragile part of an animal’s body. It can easily be damaged, and if not healed properly, an injury can lead to vision loss or infection. Getting sand, glass, or other foreign objects stuck in the eye can be very painful for many animals, who might injure themselves trying to get them out.8
Appendages like limbs, wings, and antennae can be lost directly in accidents or fights, but many animals lose appendages by self-amputation. When in danger, octopuses amputate their own arms, lizards their tails, and spiders their legs. They can do thiswhen their appendages get trapped or stuck, or in fights with other animals. They can also do it to prevent venom from a sting from spreading throughout their body, or after molting errors. When it is not to escape from a dangerous situation, self-amputation may be a response to pain resulting from an injury or an attempt to remove a useless body part.9
The degree to which a lost appendage affects an animal depends on the type of appendage, the function of the appendage, and the environment. Some animals, like octopuses and spiders, often manage well when missing an arm or a leg.10 An unhealed limb can be particularly harmful to jumping insects like crickets.11
A crayfish who only molts once a year can manage without a leg, but losing a claw or an antenna could seriously impair their ability to survive fights with other animals or to explore their environment and seek shelter.
Some vertebrates have some regenerative capacity, such as lizards who regenerate tails, different types of fishes who regrow fins, and salamanders who can regrow limbs. Bats can regenerate wings and ears and ungulates their antlers. However, the regrown parts may be smaller or weaker, and if the animal is under too much stress, they might not be able to regenerate the part at all.12
Molting is a common cause of injury in arthropods. Even when they don’t need to repair a body part, arthropods need to molt—shed their exoskeletons—in order to grow, and then their new exoskeletons must be hardened or reconstructed, together with other body parts such as the linings of organs. Although arthropods are vulnerable to external injuries during molting and while their new exoskeletons are still soft, they are more likely to die or be injured because of a fault in the complex molting process. They might also fail to regenerate an injured body part, leaving them with reduced functioning until the following molt, which might be months, or in some cases, years.13 This is worse for older animals, who tend to molt less frequently as they age.
Some larvae cannot breathe while their exoskeletons are coming off and can asphyxiate if it takes too long or something else goes wrong. For example, mayfly larvae must take in extra oxygen before they molt because they leave their tracheal lining behind and stop breathing during the molting process. In other species, just getting out of their exoskeletons can take months, and if they get stuck, they can be crushed to death as they keep growing.14
Molting arthropods can also tear off a sensitive part as they extract themselves, losing or twisting their limbs, crushing their lungs, or injuring an eye or other soft tissue. Some injuries cause life-threatening hemorrhages. Animals are more susceptible to attacks from animals of their own or other species while they are molting. For example, prawns are more likely to be injured or killed by other prawns during certain stages of molting.
An injured animal can experience intense pain and discomfort. Pain can also lead to behaviors that are dangerous to the animal, such as decreasing their intake of food and water, leading to weight loss, muscle breakdown, and impaired breathing.15 They may also be unable to eat or drink adequately to promote healing or even to stay alive.
An injured animal is also likely to suffer from a range of other problems due to infections and related diseases. In the absence of medical treatment, infection is a natural correlate of wounding in the wild. Damaged tissues also tend to become infested by parasites.16 Parasitic infestation may be extremely painful and may cause additional complications, such as diarrhea, vomiting, and visual disturbance.
Finally, the disabling effects of the injury—exacerbated by infection or parasite infestation—jeopardize the animal’s wellbeing in many important respects. The animal may not be able to escape from threatening situations or to keep up with their social group. Injured animals also become preferential targets for the attacks of other animals.17
Animals living in the wild are vulnerable to a vast array of horrific physical injuries. We’ve seen that the causes of these injuries are many and varied, including the slashes and bites of other animals; fire, ice, and torrential rains; falls and collisions; and self-amputation and molting accidents. Many of these injuries would be mild if the injured animal had a safe place to heal and adequate food and rest, but this is often not possible due to the many challenges of living in the wild.
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10 Alupay, J. S. (2013) Characterization of arm autotomy in the octopus, Abdopus aculeatus (d’Orbigny, 1834), PhD thesis, Berkeley: University of California [accessed on 12 November 2019].
11 Parle, E.; Dirks, J.-H. & Taylor, D. (2016) “Bridging the gap: Wound healing in insects restores mechanical strength by targeted cuticle deposition”, Journal of the Royal Society Interface, 13 (117) [accessed on 18 November 2019].
12 Goss, R. J. (1987) “Why mammals don’t regenerate—or do they?”, Physiology, 2, pp. 112-115; Brockes, J. P. (1997) “Amphibian limb regeneration: Rebuilding a complex structure”, Science, 276, pp. 81-87; Darnet, S.; Dragalzew, A. C.; Amaral, D. B.; Sousa, J. F.; Thompson, A. W.; Cass, A. N.; Lorena, J.; Pires, E. S.; Costa, C. M.; Sousa, M. P.; Fröbisch, N. B.; Oliveira, G.; Schneider, P. N.; Davis, M. C.; Braasch, I. & Schneider, I. (2019) “Deep evolutionary origin of limb and fin regeneration”, Proceedings of the National Academy of Sciences of the United States of America, 116, pp. 15106-15115.
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