CAUSES OF STRANDINGS
Wildlife strandings can occur for many reasons, some that the scientific community does not fully understand. This only highlights the importance of attending and studying these incidents so that we can collectively gather more data.
Many of these strandings can be prevented.
Read on to understand the causes and effects of the most understood types of marine wildlife strandings.
CAUSES: Entanglements occur when wildlife comes in contact with our waste that has been improperly disposed of in the ocean or on our coastlines. This includes active and inactive commercial fishing gear, plastic rubbish, and discarded recreational fishing gear. The entanglement occurs when the animal gets caught in a piece of debris, rope, fishing line, or net, and can't free themself from it. Over time the attached debris can snag and collect even more debris with the end result being up to thousands of pounds of man made material being dragged around by an animal. All marine wildlife can fall victim to this ugly human impact and the consequences can be fatal.
EFFECTS: Sea lions, seals, dolphins, whales, turtles, sea birds, sharks, and other fish, are often found entangled in discarded fishing gear and plastic debris that has made its way to the oceans. These entanglement can physically limit or completely restrict mobility and the animals ability to hunt or forage. Entanglement around the neck or jaw can prevent an animal from being able to eat or swallow. A seemingly benign plastic 'necklace' cuts into a sea lions flesh over time as the animal grows. Entanglements can lead to deep wounds, systemic infections, starvation, increased vulnerability to predators, and eventually death.
Cetaceans, turtles and birds often drown as a result of entanglements that trap them beneath the surface, or weigh them down and fatigue them.
All too often we see this affliction on marine wildlife. Though it can take tremendous effort to disentangle and rescue these already frightened and wary animals, our extended team of experts can sometimes pull it off. In minor cases, or with most cetaceans, the animals are cut free of the encumbering debris in the field. Pinnipeds, sea turtles, and dolphins can be brought back to MMMRC for treatment and rehabilitation if more serious damage has occurred as a result of the entanglement.
CAUSES: Injuries can occur as the result of natural behaviors, such as bite wounds from other animals, stingray barbs, or accidental falls onto rocks. Breeding adults and their young may sustain injuries during mating season, including lacerations, puncture wounds, and crushing injuries.
However, the sad reality is that some of these injuries are a result of negative human interactions. These injuries include wounds resulting from entanglement, fish hooks, gaff hooks, knives, machetes, and other intentional strikes to an animal with a sharp or blunt object. Perhaps most shocking is the number of marine mammals injured or killed by gun shot.
EFFECTS: The injuries that we see range from minor to very traumatic. In severe cases we may encounter broken bones, deeply lacerated tissue, disrupted blood supply, and even nerve damage. In addition to the traumatic injury, bacterial infections may subsequently develop. If treated early in the course of events, bacterial infections can often be eliminated, and given time and ongoing care, the traumatic injury may also resolve. In the worst cases, the animal succumbs to the trauma or needs be humanely euthanized.
CAUSES: Malnutrition leads to a large number of strandings every year. Pups that are prematurely separated from or abandoned by their mothers, or recently weaned pups that struggle to catch prey on their own, are likely to strand due to malnutrition. Likewise, larger numbers of animals, both young and adult, may strand during climatic (oceanographic) events like El Nino that cause changes in the abundance and distribution of their prey species, as well as for unknown reasons for decline in availability of prey.
EFFECTS: Malnutrition weakens an animals physical condition which leads to further complications and illnesses, including dehydration, hypoglycemia, reduced immunity, and increased vulnerability to predation. Without intervention, malnutrition will result in death. Malnourished animals may be rescued and brought to MMMRC for rehabilitation, which involves a nutrition plan, supplements, and medications as needed.
ILLNESS & DISEASE
CAUSES: Marine animals may contract a disease or develop an illness a number of ways, including natural exposure, old age, or a weakened immune system due to injury, malnutrition, or fatigue. Some ailments can be linked to environmental changes. Ingestion of fish exposed to red tide, abrupt environment changes, stress, or low food availability are some natural causes that have the potential to introduce disease. Ocean pollution, problems exacerbated by rising ocean temperatures, and the negative interactions with fishing gear can also generate problems for marine animal health that can lead to serious illness.
EFFECTS: Sea lions, dolphins and sea turtles are affected by red tides which affect the nervous system and in many cases cause irreversible damage. Malnourished, and very young or very old animals, are more likely to get sick or get an infection as their defenses are already low. Infections generated from an entanglement wound can spread rapidly and can cause systemic infection leading to death, or irreversible damage like limb loss which can pose a new set of challenges for an animal. With careful diagnosis and early detection some of these diseases can be treated. An animal may need to spend many months in rehabilitation to overcome a particular illness or disease.
CAUSES: Seals, sea lions, and dolphins are prey for large predators like sharks and Orcas (killer whales). Juvenile, and even adult whales, also fall victim to these intelligent predators and sea turtles are prey for certain shark species. But we can also look at marine mammals and sea turtles as both predator and prey, and understand that they will always fall somewhere in that circle of life. We never interfere with a natural predation event but if the the prey animal ends up stranding and we can gain access to respond, we will assist the animal on a case by case basis. Most times the wounds inflicted are too severe to effectively administer any care.
Sadly, some of these species also need to worry about predation by humans despite being protected to varying degrees by law. Once in a while we are able to intercept and treat these animals after they have been illegally poached.
EFFECTS: Strandings as a result of attempted predation are rare, because many of these incidents are fatal. Shark bites are the most common reason we would attend this type of stranding. Some bites are superficial or to the extremities and can be treated, but may impact an animals quality of life and lead to illness or malnutrition.
In many cases bites are severe and entire limbs or portions of the trunk of the body are missing. These bites often end in excessive blood loss or systemic infection, and death. If an animal is disabled by an injury that affects their mobility they may no longer be able to effectively hunt or graze.
CAUSES: Boat collisions are unfortunately something that we frequently observe in the field of marine wildlife rescue. Increased maritime traffic interferes with the natural behavior of animals, and the shipping lanes, recreational areas, and fishing zones overlap with critical animal habitats and migratory routes.
EFFECTS: Propellers from motorboats can lacerate and even dismember a marine mammal, and cut right through the carapace (shell) of a Sea Turtle. Collision with a boat can cause disorientation in dolphins and whales, causing them to strand. These injuries and strandings can result in further medical issues, including infection, disability, and death, but some of these conditions can be treated. Large cargo ships can strike whales, resulting in death. There is no means of rescue for these whales. Here in La Paz we see scars from boat propellers on many of the whale sharks that visit our bay.