Michael T. Walsh; Deke Beusse; Scott Gearhart
Sea World has been actively involved in the rescue and rehabilitation of manatees since the mid 1970's. The number of animals rescued has ranged from 1 to 27 per year with these fluctuations paralleling the number of manatees dying each year. There are eight general categories of manatee mortality which include 1) watercraft injury, 2) crushed and drown in canal locks or flood gates, 3) other human related causes such as entanglement, poaching or foreign body ingestion, 4) perinatal mortality, 5) cold stress, 6) natural disease, 7) undetermined causes, and 8) verified dead animals which are not recovered. In 1998, 231 animals died, 269 in 1999 and 273 in 2000. Watercraft injuries were responsible for 29% of the deaths while perinatal mortality accounted for 21%. 1996 was the record for manatee deaths because of an outbreak of red tide (Gymnodinium breve) that resulted in 149 deaths resulting in over 400 mortalities.
Medical and surgical management of ill or injured manatees presents numerous challenges for the clinician. Time elapse from onset of illness to presentation is often unknown and animals may be additionally compromised by severe weight loss, dehydration, constipation and foreign material ingestion. Survival rates are greatly increased by proper nutritional support, rehydration, enemas, and use of mineral oil. Antibiotic use is usually limited to parenteral administration since most oral antibiotics result in diarrhea.
Watercraft injuries are usually divided into three categories; propeller wounds, blunt trauma or combinations of both. Treatment techniques for animals with abnormal buoyancy from boat trauma have been improved with the use flotation jackets. While progress has been notable it is clear that many traumatic injuries are better approached with prevention than with treatment. This area will be better impacted with control of boat speed and decreased access to boats. Entanglement from fishing line and crab trap line is also better prevented than treated. Bandaging techniques have been modified to protect damaged flippers using Vaseline based ointments, porous tape, and superglue. Many manatees have lost limbs from self-amputation and behavioral studies are currently underway to determine those factors that may be modified to decrease this area of trauma.
Perinatal morbidity and mortality may have a substantial impact on the population when it accounts for over 20% of the deaths. Unfortunately the factors involved may be very numerous and in many cases difficult to determine. In many species there is a strong behavioral aspect incorporating genetics and other components such as bonding, nursing, and protective maternal care. Births in aquaria have illustrated that there is a wide range of maternal ability that may help to explain some aspects of survival. Some new mothers are very successful showing all of the desirable behavioral characteristics that help to insure survival. Other first time mothers may not show needed mother-calf behavior resulting in increased mortality. Some of these mothers appear to do better the second time while others may not.
For the orphan newborn manatee the clinician must provide a warm, clean environment, avoid hypoglycemia, alleviate dehydration, treat or avoid colitis or pneumatosis intestinalis, detect and treat septicemia. Research into manatee milk composition has shown that fat is the primary source of energy for the newborn. After initial stabilization with carbohydrates the hypoglycemics formula must be geared toward fat composition rather than carbohydrates. In addition the fat composition of the milk incorporates more short chain and medium chain fatty acids.
Cold stress presentations may vary with the severity of the winter. Typically the most commonly affected age class is the recently weaned. These one to three year old manatees present with a range of symptoms including weight loss, emaciation, mild to severe dermatitis and septicemia. Treatment includes warm clean water, antibiotics, rehydration, enemas and mineral oil for constipation and foreign debris, and most importantly nutritional supplementation. These individuals are often in severe negative nitrogen balance so they benefit most from tube feeding with a high calorie supplement. This is done until the weight lost is replaced and the skin lesions have healed. Those animals with frost bite like lesions may need prolonged supplementation (months) to insure proper healing. In periods of severe or extended cold water older and younger animals (usually supported by nursing) may fall victim to hypothermia. In some older individuals the skin lesions often associated with cold stress may not be evident.
Natural disease problems include infections, (parasitic, viral, bacterial, etc), birth complications, and toxins such as red tide. The potential impact of any of the possible toxins or infectious agents is unpredictable though the die off associated with red tide in 1996 illustrates the potential impacts. Viral infections, so often associated with mass mortality in many species are not well documented and further research is needed.
With so much time and financial investment in manatee rehabilitation the question most often asked is "Does it really help the survival of the manatee species?" The answer is not a simple yes or no. It is apparent that over an extended period a number of female manatees returned to the wild can contribute to the reproductive success of the species. It is also important to note that the educational value of rehabilitation for the general public is priceless to their continued success.