Robin C. Best

Thermoregulation in resting and active polar bears

SummaryPolar bears (Ursus maritimus) regulate their body temperatures both physiologically and behaviourally proportional to their level of activity while within the thermoneutral zone. Core temperatures (Tc=36.9±0.5°C at rest) varied with the 4th power of walking speed for the two subadult (220 kg) bears tested, whereas subcutaneous temperatures (Tsk=35.3±2.2°C at rest) were closely correlated withTc but also varied with wind speed (va) and ambient temperature (Ta). Radiative fur temperatures (Tr) were closely correlated withTa and negligibly withTsk. Predictive equations for these temperature relationships were derived by regression analysis. Maximum rates of heat storage (Smax) were above that predicted from the literature implying that the polar bear is an energetically costly walker. Radiative heat losses of a resting polar bear amount to between 36–67% of the metabolism and assuming a respiratory heat loss of 7–10%, convective heat losses (by difference) would thus range from 33–64%. When walking, the cooling of the fur surface by forced convection and the ‘pendulum’ effect of the moving legs of the bear lead to estimated convective heat losses on the order of 75% of the heat production while radiative losses are reduced to 13–22%. Increasing wind speeds enhance further this reciprocal effect.

Functional properties of hemoglobin and whole blood in an aquatic mammal, the Amazonian manatee (Trichechus inunguis)

Abstract 1. Hematocrit (43%) and O 2 binding capacity (18.8 ml O 2 /100 ml blood) of Trichechus inunguis blood are low compared to the values for other diving mammals but are similar to those for land mammals. 2. Stripped manatee Hb is similar to human Hb A in its sensitivity to pH, 2,3-diphosphoglycerate and CO 2 , but less sensitive to temperature and more prone to dissociate into dimers. 3. The unique Hill plots exhibit no cooperativity below 30% O 2 -saturation indicating a highly stabilized T or low-affinity state(s); such asymmetric Hill plots together with biphasic O 2 -binding kinetics could mean chain heterogeneity. 4. The pH dependence of oxygen binding by the apparent T state, hemoglobin as seen in the Hill plots, is enhanced by 2,3-diphosphoglycerate but eliminated by CO 2 .

Physiological indices of activity and metabolism in the polar bear

Abstract 1. 1. Respiratory frequency, core temperature, cardiac and stride frequencies, were evaluated as indirect indices of activity and metabolism in the polar bear ( Ursus maritimus ). 2. 2. Respiratory frequency was found inadequate as an index due to its role as a thermoregulatory effector and its “resonant” nature. 3. 3. The core temperature of the bears was highly correlated with activity or metabolic rate. 4. 4. The relationship was however curvilinear, resulting in only a 0.5°C change in core temperature over a five-fold metabolic range. 5. 5. It was impossible to accurately define different levels of activity. 6. 6. The cardiac frequencies of resting bears were extremely variable and not, as a result, good indices of these activities. 7. 7. In the active or walking animal, however, cardiac frequency is an accurate index of activity or metabolic rate. 8. 8. Stride frequency may also be used to accurately predict walking speed and, thus, metabolic rate in the polar bear.

A Radio-Tracking Study of the Amazonian Manatee Trichechus inuguis (Mammalia: Sirenia)

A juvenile male Amazonian manatee was captured in the wild, freeze-branded, and held in captivity for 20 months. It was then radio-tagged, translocated into a flood-plain lake system near Manaus, Brazil, and radio-tracked for 20 days. The study was terminated only because of logistical limitations. The 150 mHz transmitter was attached by a collar of machine belting around the caudal peduncle. Tracking was carried out by triangulation from small boats. The manatee spent almost all its time in areas where the food supply was greatest, in newly emerging aquatic vegetation near the edges of expanding lakes, and in floating meadows which were expanding as the water rose. The animal moved about 2.6 km/ day on average and was about equally active during day and night. THE AMAZONIAN MANATEE is endemic to freshwater environments of the Amazon Basin and may be found in the three primary water types of the region: white, black, and clear (Sioli 1956). Manatees occur in lakes, flood plains, and along river channels, wherever there is sufficient vegetation to sustain them (Pereira 1944). This species has a long history of exploitation, both as a food animal and, particularly during the period 1935-1954, for its extremely durable skin which was used in industry for belting material (Ferreira 1903, Carvalho 1967, Pereira 1944, Mendes 1938). During the period of intense commercial exploitation, an estimated 140,000 manatee skins were exported from Amazonia, resulting in severe depletion of manatee

O Departamento Peixe/Pesca

This paper concerns about the historic of the Fish/Fishery Department development at INPA — Instituto Nacional de Pesquisas da Amazonia. Now a day, this Department is formed by six divisions. The Division of Fishery do the evaluation of the fish stock ay using catch and landing data, field observations on catch methods, behaviour of fishing fleet, etc... The Division of Fish Biology takes place on systematic characterization of amazonian fish species, the study of food and feeding habits and reproduction according to the annual water level cycling, the differences on fish fauna related to the main types of water, as well as parasitology and icthyopathology. The Division of Aquatic Ecology analyses the limnological data of lakes and rivers of the amazonian region related to different types of water; special attention has been given to aquatic macrophites and its potential utilization in agriculture as fertilizer and cattle food. The Division of Fish Technology analyses the chemical composition of regional fishes, it develops preservation methods like as salting, drying and curing as well as quality control standards. The Division of Fish Culture develops culture methods of regional fishes, the study of natural and artificial ways of reproduction and experiments with different food formulations. The Division of Aquatic Mammals studies the biology, ecology and physiology of peixe-boi (manatee) and two species of river dolphins.