Forty-three of the 80 known species of cetaceans live around the Australian continent. These include 35 species in the Suborder Odontoceti (toothed whales) and eight species in the Suborder Mysticeti (baleen whales) (Bryden et al. 1998; Rogers 2000; Menkhorst 2001). The baleen whales include the rorquals in the Family Balaenopteridae which have longitudinal grooves in the throat and a small pointed dorsal fin.
Although most cetacean species strand, a few species regularly strand in large numbers. These include sperm (Family Physeteridae), pygmy killer (Feresa attenuata), melon-headed (Peponocephala electra), false killer (Pseudorca crassidens), short- and long-finned pilot (Globicephala spp.) and common killer whales (Orcinus orca) (Rogers 2000). The role of the veterinarian at a marine mammal stranding is presented in Chapter 3.
Three species of cetaceans are held in captivity in oceanariums in Australia: the Indo-Pacific bottle-nosed dolphin (Tursiops aduncus), the common bottle-nosed dolphin (Tursiops truncatus) and the Indo-Pacific hump-backed dolphin or sousa (Sousa chinensis). This chapter primarily deals with these species. They will be referred to here on as ‘dolphins’.
Dolphins are social animals that can live up to 50 yr. The common bottle-nosed dolphin is large, robust and uniformly mid-grey to brown without obvious stripes or colour patches. It is found throughout tropical and temperate oceans, in-shore and off-shore, in a wide variety of habitats including bays, estuaries and harbours. In Australia it is most common around the southern coast from southern Queensland to Albany in Western Australia. It is gregarious in groups of up to 20 individuals. The Indo-Pacific bottle-nosed dolphin is smaller and paler and has dark flecks on the ventral surface. It is found mainly in warm shallow in-shore waters. It is most common around the northern coast of Australia. The genetics of Australian dolphins are being investigated to determine the relationships between the many different morphometric types of bottle-nosed dolphins in Australian waters (K Charlton pers. comm.) The Indo-Pacific hump-backed dolphin is robust, uniformly pale, light grey above and whitish pink below. It is primarily found in coastal tropical and warm temperate waters, mostly less than 20 m deep in estuaries, tidal rivers and channels through mangroves. On open coasts it is often seen in the surf zone. It is gregarious in small groups of up to 25 individuals (Menkhorst 2001).
2 ANATOMY AND PHYSIOLOGY
Cetaceans share the general mammalian anatomical and physiological characteristics, with significant differences associated with adapting to a marine environment.
2.1 Digestive system
Odontocete teeth are closely spaced and uniform in shape and size and have growth rings in cross-section that can be used for ageing (Perrin & Myrick 1980). Mysticetes have a series of baleen plates suspended from each side of the upper jaw. The abdominal cavity is small and the gastrointestinal tract differs from those of terrestrial mammals. The oesophagus is penetrated dorso-ventrally by the laryngeal tube. In most cetaceans food passes either side of this structure to reach the stomach. In the pygmy sperm whale (Kogia breviceps) the left side is a blind pouch and food must pass to the right of the laryngeal tube. Dolphins and other Odontoceti have three stomach compartments and a simple but long intestinal tract. The three stomach compartments functionally correspond to regions of the stomach of monogastric mammals. The first stomach (forestomach) is an enlargement of the distal oesophagus. Digestion starts here, aided by enzymes and hydrochloric acid that refluxes from the second chamber which is the glandular or fundic stomach and is pink to red. The third is the pyloric stomach, which secretes mucus and prepares food for digestion.
The pylorus opens into a dilated pear-shaped ampulla which begins the intestinal tract. The intestinal tract of odontocetes is not visibly organised into small and large intestines, and in small species can be up to 30 m long. Mysticetes have a distinguishable colon (Geraci 2000a). Gastrointestinal transit time is very rapid, which has implications for oral drug administration. Parasites are commonly found in the stomach chambers of wild odontocetes.
2.2 Respiratory system
The upper respiratory tract has been modified to allow cetaceans to breathe at the water surface and swallow simultaneously. Complex groups of upper airway muscles in cetaceans ensure an airtight seal of the closed glottis, which is particularly important when diving. This has implications when performing bronchoscopy as it can be difficult to pass the scope. The blowhole is on top of the head and to the left of the midline in many odontocetes. In dolphins and the common killer whale it is in the midline. The blowhole is paired in mysticetes and single in odontocetes. Immediately below the blowhole in odontocetes are four pairs of nasal sacs which function in sound production. Ventral to the nasal sacs, a bony septum divides the nasal passage into left and right internal nares. The nasal passages then open into the nasopharynx, a tubular hollow space about 4–5 cm in diameter in dolphins. Projecting into the centre of the nasopharynx is the beak-like opening of the arytenoepiglottideal tube (also referred to as the goosebeak). The space between the arytenoepiglottideal tube and the pharyngeal wall is the nasopharyngeal fornix. The glottis is rosette-shaped and not covered by an epiglottis. The larynx sits in a muscular valve and together they form the arytenoepiglottideal tube. It remains tightly shut other than during respiratory cycles. The arytenoepiglottideal tube is elbow-shaped (45–80°) and joins the trachea caudally. The trachea has complete tracheal rings (Harper et al. 2001; Tsang et al. 2002) (Fig. 18.1). This anatomical arrangement has important implications for intubation for inhalation anaesthesia. The lungs are large, adapted for deep diving and turgidly elastic and the pleura is thick and well-vascularised. Cartilaginous rings continue down to the origin of the alveoli, making the lungs rigid and resilient (Geraci 2000a).
Figure 18.1 Upper respiratory and oesophageal anatomy of a dolphin. a) Blowhole. b) Nasal sacs. c) Nasal passages (paired). d) Nasopharynx. e) Arytenoepiglottideal tube. f) Nasopharyngeal fornix. g) Trachea. h) Oesophagus.
2.3 Cardiovascular system
The dolphin heart is large relative to body mass. The ventricles are thick-walled and highly trabeculated. There are numerous retia mirabile in the thorax and head. Peripheral venous retia help regulate body temperature. Surface arteries (particularly in the flukes, flippers and dorsal fin) are surrounded by a network of veins encased in a rigid channel of connective tissue underlying the dermis (Fig. 18.2). To retain body heat, arterial blood flows to the surface under low pressure and returns along the surrounding venous rete, absorbing heat from the central artery. To cool, blood flows under high pressure, thereby collapsing the surrounding veins against the rigid tunnel walls, and returns by superficial veins that lie closer to the surface of the skin. These vessels in the flukes are useful for venipuncture (Geraci 2000a).
Figure 18.2 i) Blood vessels and the peripheral venous retia in the tail fluke, epidermis (a), dermis (b), connective tissue (c), vein (d), dense connective tissue core (e), artery (f), periarterial venous retia (g). ii) Conserving heat. iii) Cooling. (Source: After Geraci (1986a), Geraci & Lounsbury (1993).)
The liver has a prominent dividing cleft and large intrahepatic sinuses. There is no gall bladder. The spleen is ovoid, small (4–8 cm) and firm and there may be one or more smaller accessory spleens. The kidneys are elongated and hyperlobulated (multirenculate).
2.5 External features
Cetaceans do not have external ears but have small openings in the sides of the head directly behind each eye. The large eyes have flattened corneas for underwater vision. There are no hind limbs and the fore limbs are modified into a flipper. The skin is smooth and rubbery and generally lacks hairs and glands. The row of bristle-like hairs along the snout of newborn cetaceans is lost within a few weeks of birth. Rorquals have a sparse beard along the chin (Geraci 2000a).
Dolphins’ normal respiratory rate is 1–3 breaths per minute. Normal heart rate is 50–90 beats per minute. Normal rectal temperatures range from 35°C–37°C. The temperature of cetaceans can be assessed by inserting a sensor probe 10–15 cm into the rectum. The body temperature may fluctuate and this should be considered when using body temperature to clinically evaluate a cetacean.
2.6.1 Water balance
The osmotic concentration of sea water is about four times that of mammalian body fluids, which favours loss of body fluids. Cetaceans have evolved a number of strategies to compensate for this: the skin is impermeable to sea water, little water is lost through the respiratory tract or by evaporative cooling, and water is conserved by concentrating milk and urine. Cetaceans obtain water from their diet (free-formed water and metabolic water from oxidation of fat) and do not require an additional source. However, they can and do drink water they swim in.
Marine mammals secrete large amounts of aldosterone in response to stress. Aldosterone promotes the reabsorption of sodium from the renal tubules, drawing water back into the body. This mechanism conserves water when food is not available or the animal is not eating (Geraci 2000a).
Most cetaceans live in an environment that is significantly cooler than their body temperature. Cetaceans have developed several mechanisms to deal with the fact that heat is conducted about 20 times faster in water than in air. The large body size and small appendages results in low surface area to volume ratios. Therefore they have a large body core to produce heat but only a small surface area to lose it. Blubber, a meshwork of connective tissue that supports fat cells, acts as a very effective insulating layer just beneath the skin.
The peripheral venous retia function as a counter-current heat exchange mechanism in both warm and cold environments (Fig. 18.2). Core body temperature is conserved by selective vasoconstriction of superficial vessels that would otherwise dissipate heat. In cold environments core body temperature of cetaceans can drop by about 2°C, thus lowering the temperature gradient between external and internal environments (Geraci 2000a).
In extremely cold water the surface tissues are kept active partly by cold-adapted isoenzymes in cells and the large unsaturated fatty acid component of blubber (Geraci 2000a).
2.6.3 Adaptations for diving
Cetaceans exhale when they dive to great depths. At about 100 m the lungs are almost totally collapsed. The residual air is forced into dead air spaces from which nitrogen cannot diffuse into the circulation. The ribcage is flexible and can collapse without injury. The cartilaginous airways prevent crushing of the lungs and allow them to open quickly when returning to the surface. The numerous retia mirabile engorge when diving to counter the pressure on the thorax, ears and nasal sinuses. At depths there is no gas exchange in the lungs as they are collapsed. Instead the lungs are adapted for rapid and efficient extraction of oxygen when inflated. The oxygen is circulated in the large volume of haemoglobin-rich blood.
During longer dives heart rate slows significantly. There is peripheral vasoconstriction with shunting of blood away from the skin, muscle and abdominal viscera. Body temperature decreases. Stored oxygen is directed to the brain and heart. Oxygen is stored in myoglobin and can be released during long dives. Accumulation of carbon dioxide does not trigger respiration as it does in terrestrial mammals. After an anaerobic dive the animal must remain at the surface for a long time to recover.
There are no external genitalia in males. The genders can be distinguished by features of the genital slits. The male has a separate anal slit behind the genital slit. The female has a longer and more prominent slit which encompasses the more closely spaced genital and anal openings. Internally, the genital slit in the female is directed cranially while in the male it is directed caudally (Geraci 2000a). The testes are internal and are very large compared to those of most terrestrial mammals of similar body size. Veins carrying cool blood from the dorsal fin and flukes are juxtaposed to arteries supplying the testes. This allows the production and storage of sperm at a cooler temperature.
Male dolphins generally reach sexual maturity at about 8–10 and females at 10–12 yr of age. Captive animals may reach sexual maturity earlier due to increased food availability. Mature sperm was found in semen obtained from a 2 yr old male bottle-nosed dolphin (H Muraco pers. comm.) but this is probably an exception.
Dolphins in Australian waters appear to breed year-round, with a peak of births in summer.
Dolphins in captivity in Australia are polyoestrus with peaks in sexual activity and births in summer. Ovulation is spontaneous, with an oestrous period of about 21 d. Gestation lasts 12 mo, after which a single offspring is born. Calves are normally born tail first, weigh about 10 kg and are 98–126 cm long. Lactation lasts 12–18 mo and the young become independent around 2–3 yr of age. Lactation may suppress oestrus. Female offspring stay with the mother and the maternal pod for a long time. Male offspring generally leave the maternal pod and form pairs or live singly, interacting with female pods only for breeding.
Many dolphins seem to adapt well to captivity. They are active, intelligent and inquisitive and their housing and husbandry must meet their behavioural and physical requirements. Housing standards have been developed for captive cetaceans in Queensland (Queensland Wildlife Parks Association 2003) and New South Wales (Department of Primary Industries 2005). These standards cover minimum space, containment structures, water and climatic conditions.
Ideally dolphins should be kept in natural sea water. Artificial salt water can be used but is expensive and there may be problems with the availability of the constituents. Dolphins fare better in natural outdoor enclosures. Indoor enclosures are associated with a higher incidence of disease, particularly respiratory disease. Pool construction can be natural or artificial. If artificial (concrete, fibreglass) the enclosure should be durable, watertight, non-porous, non-abrasive, non-toxic and easily cleaned and disinfected. Sharp projections and loose fittings should be avoided. Water quality is easier to maintain in artificial pools and there are fewer opportunities to encounter foreign objects, such as stones that may be ingested, than in natural pools. Natural pools (i.e. dug into natural substrate or a netted natural marine water body) can be constructed much larger for less cost than artificial pools. The pools should be large enough to accommodate the natural behaviours of the animals and deep enough for them to dive and avoid the effects of ultraviolet radiation. The water should be shaded and the temperature maintained between 15°C–30°C. If chemical treatment is used to maintain water quality and cleanliness, it should not harm the animals. Many different disinfection systems have been used. Chlorine and ozone are the most common. Both are suitable as long as the water quality is monitored carefully and regularly. As dolphins live entirely in water, water quality is critical to maintain healthy animals (Arkush 2001; see Chapter 17, 4.3). Table 18.1 shows important water parameters and their acceptable levels.
Cetaceans are very amenable to training and a number of behaviours can be trained to assist in their management. Behaviours that can be trained include eye examinations and instillation of medications, rectal temperature recording, presentation for ultrasonographic examination, and collection of blood, urine, stomach fluid, semen or faeces. Animals can be conditioned to haul out onto scales to measure body weight regularly. This is extremely useful and animals should be weighed at least monthly (preferably weekly) to objectively assess body condition.
4.3 Estimating body weight
If weighing scales are not available, an equation can be used to estimate normal body weight (ENBW) by measuring the animal’s length (Bedford 2000). For common bottle-nosed dolphins the equation is:
ENBW = (1.616 × body length in cm) — 236
For Indo-Pacific bottle-nosed dolphins it is:
Log ENBW = (0.1389 ×log body length32019)
Normal adult body weights for the Indo-Pacific bottle-nosed dolphin are 120–170 kg for males and 110–150 kg for females; for the common bottle-nosed dolphin 180–230 kg for males and 170–220 kg for females; and for the Indo-Pacific hump-backed dolphin 220–250 kg for males and 160–200 kg for females. Body weights fluctuate seasonally with animals tending to be heaviest in winter and lightest in summer, generally corresponding with food intake. Body condition can be assessed visually by experienced observers. Severe and pathological weight loss is evident when the ribs are easily seen and the muscles along the dorsal thorax are wasted, giving a concave shape lateral to the midline. Any sudden or unexpected weight loss should be investigated.
4.4 Individual marking and identification techniques
Generally, animals are identified by their markings or other obvious physical differences, including the shape of the rostrum, the shape and outline of the dorsal fin, and visible scars. Microchips or passive integrated transponder (PIT) tags can be inserted IM to identify individuals. A suitable site for implanting is the muscle just caudal and lateral to the dorsal fin. Implanting on the left side is the standard.
Purpose-made padded stretchers with openings through which the flippers can protrude and openings in the genital region to prevent urine scalding are ideal. Stretchers without these openings should be used only for short periods (20 min) to avoid crushing the flippers and overheating. The fabric of the stretcher should be smooth and easily disinfected. Cetaceans should always be transported in ventral recumbency, never in lateral recumbency. The stretcher can be suspended in a water-filled container for long trips with the dorsal surface exposed to the air so the animal can breathe. Foam padding will help protect and support the animal. Transport time should be minimised. Keep the animal wet by lying moist towels or sheets over it or by continuously spraying with water. Never cover or fill the blowhole with water. Temperatures during transport should not exceed 30°C or be less than 15°C. Overheating is more of a problem than cold. It may be useful to have a supply of ice on hand. Always protect the animal from direct sunlight, wind and exhaust fumes. Never roll cetaceans to move them as this distresses them greatly and may damage the flippers and dorsal fin. A small crane fixed to the transport vehicle or separate is useful for lifting heavy animals.
Cetaceans should never be transported free in a water-filled container as there is a risk of drowning or hitting the side of the container and causing serious injury.
The use of sedatives when transporting cetaceans is debatable. Unless the animal is highly agitated it may be better to forgo the use of these agents, as they can cause respiratory depression and affect thermoregulation. Midazolam (0.04–0.06 mg/kg) has been used routinely at one institution when transporting potentially stressed animals, without side effects (D Spielman pers. comm.).
Wild bottle-nosed dolphins eat mostly fish and squid. Indo-Pacific bottle-nosed dolphins eat fish from inshore reefs and sandy benthic habitats while Indo-Pacific hump-backed dolphins eat mostly fish, some squid and crustaceans (Menkhorst 2001). Wild and captive Indo-Pacific hump-backed dolphins have been seen catching and eating birds.
Captive dolphins are primarily fed fish at least three times a day. A variety of species should be fed daily as different species have different nutritional content varying with sex, season, handling and storage. Whole fish rather than fillets or cleaned gutted fish should be fed. The calcium in the bones, vitamin A in the liver and fats in the gonads are all essential in a balanced diet. As a rough guide, captive animals should be fed 5–7% of their body weight daily. This should be increased in pregnant, lactating and growing animals. Captive dolphins, like other species in captivity, have a tendency to become obese and therefore body weight should be monitored and controlled.
Most fish fed to captive dolphins has been frozen, which is important in killing parasites in fish. The appropriate storage and thawing of frozen fish is important to maintain nutrient content and quality (Geraci & St Aubin 1980; Geraci 1986b). The ideal thawing conditions to maintain hydration and nutrients are in an airtight container at 4–8°C. Thawing fish in water leaches essential vitamins and minerals from the fish. Fish contain thiaminases that destroy thiamine. Fat-soluble vitamins are also readily lost. All fish should be supplemented daily with vitamin E (50 IU/kg of fish fed) and thiamine (20 mg/kg of fish fed). These supplements can be given as tablets or capsules in the fish, and various commercial products are available (see Chapter 17). Because of the short transit time of food in the gastrointestinal tract, supplements should be easily digestible.
An artificial diet was formulated in the US using traditional fish feed industry ingredients and proved palatable in trials. However, the animals needed 25% more of the artificial diet on a daily weight basis to maintain weight (Wright et al. 2005). It could be useful if storage space is a problem or supplies of fish are disrupted.
When free-ranging cetaceans are brought into captivity they may not eat dead fish for several days and may require force-feeding if they are in poor condition. Force-feeding is easy. Restrain the animal, open the jaws using soft rope or rolled-up towels around each jaw and introduce the fish deep into the oesophagus. Because of the nature of cetacean anatomy there is no risk of food entering the respiratory tract.
See Chapter 17, section 5, for additional information on nutrition.
Handling and restraining captive cetaceans is frequently required to facilitate moving animals between facilities or to conduct routine husbandry or veterinary procedures. There is always potential for injury to both animal and people so it is important that the procedures be carried out only by appropriately trained handlers. Many procedures can be performed using operant conditioning, making them safer and less stressful for animal and handlers. A training program to facilitate transportation and handling should be incorporated into the husbandry program of all captive dolphins.
6.1 Physical restraint
Cetaceans are often physically restrained. They can be herded into small shallow areas where they are easier to catch. Small cetaceans can be restrained by grabbing them from above and pushing both pectoral fins against the body. Once restrained, they can be placed on a smooth flat surface. If restraint will exceed 10–15 min they should be positioned on foam pads (7.5–10 cm thick) or mattresses to alleviate pressure on the stomach and lungs. Even wild animals tolerate physical restraint and can be restrained for up to 3 hr without undue stress as long as environmental conditions are suitable and appropriate supportive care is provided. Restraint is rarely required for longer than 90 min. Always take care with the tail as it can cause significant injury to handlers if it hits them. Dolphins can bite and their teeth are sharp. They can also damage themselves if not appropriately restrained. Keep them cool and wet while restrained, but if they are being sprayed or hosed with water ensure it does not enter the blowhole. Do not subject them to long periods of direct sunlight—they can suffer sunburn in 30 min under Australian conditions. If the procedure is likely to take longer than this, erect a shade shelter.
6.2 Chemical restraint
Cetaceans are rarely chemically restrained. Many procedures such as dentistry, endoscopy and minor surgery can be accomplished by combining sedation and local anaesthesia. Sedatives that are useful in captive cetaceans include midazolam (0.095 mg/kg IM) and diazepam (0.15–0.2 mg/kg IM). Responses to both drugs vary between individuals. Sedated animals should be monitored closely and kept separate until the effects of the sedative have worn off. Both drugs can be reversed by flumazenil (0.002–0.004 mg/kg IM or IV). Butorphanol has also been used at 0.05–0.2 mg/kg IM with reasonable results (Chittick et al. 2006). The effects of butorphanol can be reversed by naltrexone (0.3 mg/kg IM).
General anaesthesia is rarely performed in cetaceans. It can be done successfully but is logistically difficult. Induction can be accomplished IM or IV (see 7.1 and 13). IV agents include thiopentone (15–20 mg/kg), propofol (3.5–4.8 mg/kg) or tiletamine/zolazepam (1–2 mg/kg). Tiletamine/zolazepam may be the agent of choice as it is not irritant perivascularly. IM agents include tiletamine/zolazepam (2–2.5 mg/kg) and medetomidine (0.04 mg/kg) plus ketamine (2 mg/kg). Medetomidine can be reversed with atipamazole (0.2 mg/kg IM). Intubation is achieved by dislocating the modified larynx (arytenoepiglottideal tube) from the nasopharyngeal sphincter of the blowhole by reaching into the mouth and intubating blindly via the oral cavity (Fig. 18.1). Laryngospasm does not occur. The diameter of the trachea is large and adult dolphins require a 24–32 mm endotracheal tube. The bifurcation of the trachea is more cranial in cetaceans and care must be taken to avoid introducing the endotracheal tube into either bronchus. Maintain gaseous anaesthesia with intermittent positive pressure ventilation, ensuring the chest makes normal excursions. Useful inhalation agents include isoflurane, sevoflurane or desfurane in oxygen. Anaesthesia should be monitored for oxygen saturation, pulse rate, end tidal carbon dioxide concentration and minimum anaesthetic concentration. End tidal carbon dioxide levels should be kept below 40 mmHg by the rate and depth of ventilation.
7 CLINICAL PATHOLOGY
7.1 Haematology and Biochemistry
7.1.1 Sample collection
Numerous sites can be used for venipuncture in cetaceans (Fig. 18.3), but the preferred site in most cetaceans are vessels that run along grooves parallel to the leading edge of the tail fluke near the midline on the flukes’ dorsal and ventral surfaces. The groove can be palpated or seen and is often more prominent on the ventral surface. These vessels comprise a superficial vein and a deeper artery surrounded by a periarterial venous rete (Fig. 18.2). Blood may be collected from either and it may be difficult to determine which vessel has been entered. A 23 G scalp vein set can be inserted perpendicularly or at a slight angle to the skin into the vessels and blood can be aspirated into a syringe. Ideally, captive cetaceans should be trained to present their tail flukes for unrestrained blood collection (Fig. 18.4).
Cetacean blood clots slowly so a significant sample can be collected from even a poor flow. Partial prothrombin time is long in dolphins because of a lack of Factor XII and plasma prekallikrein, which disables the intrinsic pathway of the coagulation cascade (Bossart et al. 2001). Captive dolphins should be bled regularly (at least six-monthly preferably monthly) for routine haematological and biochemical analyses. This provides invaluable reference data for individual animals and allows the detection of subclinical disease.
7.1.2 Reference ranges and interpretation
Haematology and serum chemistry are extremely useful in monitoring the health of captive cetaceans. The peripheral blood of cetaceans readily reflects systemic pathological processes, particularly inflammation. Changes are similar to those seen in domestic companion animals, which may be used to guide interpretation. However, a number of factors have been shown to influence haematology and biochemistry values in dolphins. These include gender, age, nutrition, stress, habitat, diving capacity and seasonality. These need to be considered when interpreting results (Fair et al. 2006). Pelagic species have been shown to have higher RBC counts, PCV and haemoglobin concentration than those residing in coastal environments. This is thought to be due to the greater physiological oxygen demand on deeper-diving off-shore dolphins (Duffield et al. 1983). In a study by Fair et al. (2006), non-pregnant female dolphins were shown to have higher mean triglyceride concentrations than males had. In another study, overall serum creatinine levels were found to be 15–38% higher in summer than in winter. Cholesterol levels were also found to be seasonally variable, with values ranging from 96–348 mg/dL. The highest levels recorded were for adult females in spring (244.9 ± 27.9 mg/dL) and males and juveniles in winter (177.5 ± 40.1 mg/dL, 219.1 ± 39.3 mg/dL). Overall free fatty acid levels peaked in summer (0.610 ± 0.191 mEq/L for adult males, 0.789 ± 0.309 mEq/L in adult females and 0.547 ± 0.151 mEq/L in juveniles) and dropped off in winter (Terasawa et al. 2002). Significantly higher fibrinogen levels have been observed in pregnant dolphins than in non-pregnant dolphins. Plasma creatinine levels can be higher in males than in females (Fair et al. 2006). In general, RBC counts are higher in neonates than in adults; they decrease during growth and as the individual starts to dive (Reidarson 2003). Younger dolphins also tend to have higher levels of CK than adults do. Adult dolphins have been shown to have higher concentrations of AST, alpha-1, alpha-2 and gamma globulins, and total protein than juveniles (Fair et al. 2006). Stress and handling time may affect blood parameters such as glucose, TCO2 and HCO3, with these increasing with longer duration of handling (Varela et al. 2006).
As in all mammals, an increased PCV and haemoglobin concentration generally reflects dehydration and low PCV indicates either blood loss or reduced red cell production. In cetaceans in general, mild normocytic anaemia can be associated with infection, and microcytic anaemia can be indicative of haemorrhagic gastric and duodenal ulcers. Leukocytosis is often associated with tissue damage in dolphins, and large increases above normal of up to 40% are a common finding in individuals post transport. Neutrophilia is a common finding with infection. A high neutrophil count (>10 000 ×109/L) may indicate fungal or bacterial infection. Lymphopaenia (<1000 ×109/L) may infer viral infection. Chronic infections are normally correlated with increases in monocytes and lymphocytes (Medway & Geraci 1986). Numbers of circulating eosinophils are significantly lower in captive than in free-ranging animals, most likely due to the reduced numbers of parasites in captive animals (Reidarson 2003). In general, it has been reported that red blood cell count is lower in aquatic mammals than in terrestrial mammals (Shirai & Sakai 1997).
ALP levels have been shown to be affected by age, with higher levels in rapidly growing younger animals whose bones are undergoing ossification. Consequently ALP levels can be used as an indicator of bone metabolism (Fair et al. 2006). ALP is also a useful indicator of nutritional status in dolphins and other cetaceans due to its positive correlation with increasing body weight. However, increased ALP levels are rarely associated with liver pathology in cetaceans, unlike in terrestrial mammals (Reidarson 2003). Potassium levels in dolphins can increase following rigorous exertion. Glucose levels in cetaceans are generally higher than in other mammals. This may be due to the need for adequate glucose levels in the brain during the deep and extended periods of diving exhibited by many cetaceans (Medway & Geraci 1986). Electrolyte values combined with total protein and albumin values can be used to evaluate hydration status. Dehydration should be suspected when the albumin level exceeds 40 g/L and the PCV exceeds 0.48. These should be interpreted in conjunction with other results.
Table 18.2 provides haematology and biochemistry values for dolphins.