Dive Performance Research Articles

Determining effective subject-specific strength levels for forward dives using computer simulations of recorded performances

This study used optimisation procedures in conjunction with an 8-segment torque-driven computer simulation model of the takeoff phase in springboard diving to determine appropriate subject-specific strength parameters for use in the simulation of forward dives. Kinematic data were obtained using high-speed video recordings of performances of a forward dive pike (101B) and a forward 2 1 2 somersault pike dive (105B) by an elite diver. Nine parameters for each torque generator were taken from dynamometer measurements on an elite gymnast. The isometric torque parameter for each torque generator was then varied together with torque activation timings until the root mean squared (RMS) percentage difference between simulation and performance in terms of joint angles, orientation, linear momentum, angular momentum, and duration of springboard contact was minimised for each of the two dives. The two sets of isometric torque parameters were combined into a single set by choosing the larger value from the two sets for each parameter. Simulations using the combined set of isometric torque parameters matched the two performances closely with RMS percentage differences of 2.6% for 101B and 3.7% for 105B. Maximising the height reached by the mass centre during the flight phase for 101B using the combined set of isometric parameters and by varying torque generator activation timings during takeoff resulted in a credible height increase of 38 mm compared to the matching simulation. It is concluded that the procedure is able to determine appropriate effective strength levels suitable for use in the optimisation of simulated forward rotating dive performances.

Tracking leatherback turtles ( Dermochelys coriacea) during consecutive inter-nesting intervals: Further support for direct transmitter attachment

Over recent years there have been substantial efforts to record and interpret the post-nesting movements of leatherback turtles ( Dermochelys coriacea) breeding in tropical regions. Less well documented are the movements undertaken by individual turtles during the breeding season itself, or more specifically between sequential nesting events. Such movements are of interest for two reasons: (1) gravid female leatherbacks may range extensively into the territorial waters and nesting beaches of neighbouring countries, raising questions for conservationists and population ecologists; and (2) the magnitude of movements themselves help elucidate underlying reproductive strategies (e.g. whether to rest near to the nesting or forage extensively). Here, satellite relay data loggers are used (SRDLs) to detail the movements and behaviour of two female leatherback turtles throughout three consecutive inter-nesting intervals in the Commonwealth of Dominica, West Indies. Both near-shore residence and extensive inter-nesting movements were recorded, contrasting previous studies, with movements away from the nesting beach increasing towards the end of the nesting season. Using this behavioural study as a backdrop, the suitability of attaching satellite transmitters directly to the carapace was additionally explored as an alternative approach to conventional harness deployments. Specifically, the principal aims were to (1) gather empirical data on speed of travel and (2) assess dive performance (aerobic dive limit) to enable comparisons with turtles previously fitted with harnesses elsewhere in the Caribbean ( n = 6 turtles; Grenada, WI). This produced mixed results with animals bearing directly attached transmitters travelling significantly faster (55.21 km day − 1 ; SD 6.68) than harnessed individuals (39.80 km day − 1 ; SD 6.19); whilst no discernable difference in dive performance could be found between the two groups of study animals.

Is mass loss in Brünnich's guillemots Uria lomvia an adaptation for improved flight performance or improved dive performance?

Breeding Brünnich's guillemots Uria lomvia show stepwise mass loss at the time of hatch. This mass loss has usually been explained as an adaptation to reduce the cost of flight during the chick‐rearing period because flight time increases during that period. It is possible, however, that mass loss also increases dive performance during the chick‐rearing period because time spent diving also increases during that period. Reduced mass could reduce basal metabolic rate or costs associated with buoyancy and therefore increase aerobic dive limit. To examine the role of mass loss in dive behavior, we attached time‐depth‐temperature recorders for 24–48 h to chick‐rearing and incubating Brünnich's guillemots at Coats Island, Nunavut (2005: n=45, 2006: n=40), and recorded body mass before and after each deployment. There was no relationship between mass and dive duration during either incubation or chick‐rearing. Seventeen of the birds we sampled during incubation were resampled during chick‐rearing. For this group, dive duration increased with mass loss between incubation and chick‐rearing (r2=0.67–0.75). Mass loss occurred through reductions in metabolically‐active tissues (liver, bladder) and buoyant tissues (lipids) although muscle and gut mass did not change. Despite the large change in lipids, buoyancy only changed by 0.1%, and mass loss therefore did not have much effect on costs associated with buoyancy. Nonetheless, surface pause duration for a given dive depth decreased during chick‐rearing, supporting the idea that reduced mass led to increased aerobic dive limit through reduced metabolic rate and inertial costs; oxygen stores did not increase. We also attached neutrally (n=9) and negatively (n=11) buoyant handicaps to the legs of adults to assess the effect of artificial mass increases on time budgets. Artificially increasing mass decreased total time spent diving but did not change time spent flying. There was no change in shift length between incubation and chick‐rearing, and therefore no support for the idea that mass loss reflected a change in fasting endurance requirements. An energetic model suggested that the observed mass reduction reduced dive costs by 5–8% and flight costs by 3%. We concluded that mass loss may be as important for increasing dive performance as increasing flight performance.

Biomechanical Comparison of the Track Start and the Modified One-Handed Track Start in Competitive Swimming: An Intervention Study

This study compared the conventional track and a new one-handed track start in elite age group swimmers to determine if the new technique had biomechanical implications on dive performance. Five male and seven female GB national qualifiers participated (mean +/- SD: age 16.7 +/- 1.9 years, stretched stature 1.76 +/- 0.8 m, body mass 67.4 +/- 7.9 kg) and were assigned to a control group (n = 6) or an intervention group (n = 6) that learned the new one handed dive technique. All swimmers underwent a 4-week intervention comprising 12 +/- 3 thirty-minute training sessions. Video cameras synchronized with an audible signal and timing suite captured temporal and kinematic data. A portable force plate and load cell handrail mounted to a swim starting block collected force data over 3 trials of each technique. A MANCOVA identified Block Time (BT), Flight Time (FT), Peak Horizontal Force of the lower limbs (PHF) and Horizontal Velocity at Take-off (Vx) as covariates. During the 10-m swim trial, significant differences were found in Time to 10 m (TT10m), Total Time (TT), Peak Vertical Force (PVF), Flight Distance (FD), and Horizontal Velocity at Take-off (Vx) (p < .05). Results indicated that the conventional track start method was faster over 10 m, and therefore may be seen as a superior start after a short intervention. During training, swimmers and coaches should focus on the most statistically significant dive performance variables: peak horizontal force and velocity at take-off, block and flight time.

WHAT GROUNDS SOME BIRDS FOR LIFE? MOVEMENT AND DIVING IN THE SEXUALLY DIMORPHIC GALÁPAGOS CORMORANT

Flightlessness in previously volant birds is taxonomically widespread and thought to occur when the costs of having a functional flight apparatus outweigh the benefits. Loss of the ability to fly relaxes body mass constraints which can be particularly advantageous in divers, because underwater performance correlates with mass. The Galápagos CormorantPhalacrocorax harrisiis flightless and the largest of its 27‐member genus. Here, the loss of flight, and consequent reduced foraging range, could be compensated by enhanced dive performance. Over three years, 46 Galápagos Cormorants were successfully equipped with time–depth–temperature recorders, and 30 birds with GPS recorders during the breeding season. Birds foraged at a mean of 690 m from the nest and just 230 m from the nearest coast, confirming an extremely limited foraging range during the breeding season and corresponding increased potential for intraspecific competition. Although the maximum recorded dive depth of 73 m tallied with the species body mass, &gt;90% of dives were conducted in water &lt;15 m deep. The heavier males foraged in different areas and dived longer and deeper than females, which exposed males to colder water. Consideration of how plumage insulation decreases with depth indicates that diving males should lose 30% more heat than females, although this may be partially compensated by their lower surface area : volume ratio. A simple model highlights how energy expenditure from swimming underwater due to buoyancy and energy lost as heat have opposing trends with increasing depth, leading to the prediction of an optimum foraging depth defined by the volume of plumage air and water temperature. This has ramifications for all diving seabirds. It is proposed that the reduction in wing size, together with energy‐expensive flight musculature, allows the Galápagos Cormorant to be more efficient at shallow depths than other seabirds, but only in warm equatorial waters. The high prey density and predictability of benthic prey in defined areas of the Galápagos can be particularly well exploited by this flightless species, with its limited foraging range, but the Galápagos Cormorant is unlikely to be able to accommodate much change in environmental conditions.

Juvenile Steller sea lion dive behavior following temporary captivity

Wild-caught juvenile Steller sea lions Eumetopias jubatus (n = 21) were maintained in temporary captivity for up to 12 wk to investigate health, disease, nutrition and behavior. We assessed the effects of captivity on post-release dive behavior and movement of each animal using externally mounted satellite data recorders. Based on a 74.1 ± 9.6 (SE) d tag transmission period, the mean dive depth (26.2 ± 4.0 (SE) m), dive duration (1.4 ± 0.1 (SE) min), dive rate (10.1 ± 0.5 (SE) dives h 1 ), trip duration (10.8 ± 0.7 (SE) h), haul-out duration (11.3 ± 0.9 (SE) h) and time wet (46.9 ± 2.6 (SE)%) were within the range of previously published values. Movement (190.0 ± 31.9 (SE) km) between haul-outs and rookeries during the tracking period was also typical of juvenile Steller sea lions in Alaska. This study indicates that temporary captivity has little or no detrimental effect on dive performance or movement in the tracking period following release.

Estimating field metabolic rates of pinnipeds: doubly labelled water gets the seal of approval

Summary 1. Measures of the field metabolic rate of marine mammals are extremely difficult to make but they are essential for assessing the impacts of marine mammals on prey populations, and for assessing dive performance in relation to aerobic limits. 2. The doubly labelled water (DLW) method is an isotope-based technique for the estimation of the CO 2 production, and hence energy expenditure, of free-living animals. Estimates of field metabolic rate (FMR) from DLW in pinnipeds to date are extremely high and at the upper range for most mammals. DLW has previously been validated in pinnipeds but logistical difficulties meant for these validations were less than ideal, and it has been hypothesised that DLW may overestimate FMR in these animals. 3. To test this hypothesis, we used DLW and simultaneous open-flow respirometry to determine the daily energy expenditures (DEE) of wild grey seals ( Halichoerus grypus ) held temporarily in a captive facility, during 4‐5 days of simulated foraging at sea. Comparing DEE from DLW and respirometry, we found that DLW predicted DEE accurately (average difference between the two estimates was 0·7% SD = 17% n = 31), but as with validations of other species there was a large range of individual errors (from ‐39% to +44%). 4. The results dispel the doubts surrounding the use of DLW as a field method for estimating energy expenditure in grey seals, and by implication other pinnipeds, and simultaneously open a series of questions about their ability to maintain surprisingly high metabolic rates for protracted periods. 5. We make a number of recommendations for future studies of pinniped FMR using DLW. We suggest use of the Speakman two-pool calculation will be most appropriate. Studies should aim for enrichment levels as high as economically feasible but to at least 150 p.p.m. above background for the O 2 isotope. Measurement periods should be extended between one and two half-lives (5‐10 days for a typical foraging seal). We also encourage the calculation and presentation of estimates of precision in estimates of FMR.

Allometry of diving capacities: ectothermy vs. endothermy

Body mass positively influences diving capacities in air-breathing vertebrates and has been identified as a key determinant for the evolution of diving. Our review on the relationship between body mass and dive duration (a major parameter of dive performances) encompassed for the first time a wide diversity of air-breathing vertebrates. We included a substantial number of nonavian and nonmammalian diving species belonging to various independent lineages (sea snakes, iguana, turtles and crocodiles). Our analyses suggest that the widely accepted size dependency of dive duration applies with significantly less force in ectotherms compared with endotherms; notably we failed to detect any effect of body mass in ectotherms. We hypothesize that the absence of tight physiological links between body mass and respiratory demands documented in ectotherms blurred our ability to detect the expected correlation. Further exploration of the evolution of diving physiology may well necessitate adopting novel perspectives to encompass both ectothermic and endothermic modes.

To what extent might N2 limit dive performance in king penguins?

A mathematical model was used to explore if elevated levels of N2, and risk of decompression sickness (DCS), could limit dive performance (duration and depth) in king penguins (Aptenodytes patagonicus). The model allowed prediction of blood and tissue (central circulation, muscle, brain and fat) N2 tensions (P(N2)) based on different cardiac outputs and blood flow distributions. Estimated mixed venous P(N2) agreed with values observed during forced dives in a compression chamber used to validate the assumptions of the model. During bouts of foraging dives, estimated mixed venous and tissue P(N2) increased as the bout progressed. Estimated mean maximum mixed venous P(N2) upon return to the surface after a dive was 4.56+/-0.18 atmospheres absolute (ATA; range: 4.37-4.78 ATA). This is equivalent to N2 levels causing a 50% DCS incidence in terrestrial animals of similar mass. Bout termination events were not associated with extreme mixed venous N2 levels. Fat P(N2) was positively correlated with bout duration and the highest estimated fat P(N2) occurred at the end of a dive bout. The model suggested that short and shallow dives occurring between dive bouts help to reduce supersaturation and thereby DCS risk. Furthermore, adipose tissue could also help reduce DCS risk during the first few dives in a bout by functioning as a sink to buffer extreme levels of N2.

Allometric scaling of lung volume and its consequences for marine turtle diving performance

Marine turtle lungs have multiple functions including respiration, oxygen storage and buoyancy regulation, so lung size is an important indicator of dive performance. We determined maximum lung volumes ( V L) for 30 individuals from three species ( Caretta caretta n = 13; Eretmochelys imbricata n = 12; Natator depressus n = 5) across a range of body masses ( M b): 0.9 to 46 kg. V L was 114 ml kg −1 and increased with M b with a scaling factor of 0.92. Based on these values for V L we demonstrated that diving capacities (assessed via aerobic dive limits) of marine turtles were potentially over-estimated when the V L-body mass effect was not considered (by 10 to 20% for 5 to 25 kg turtles and by > 20% for turtles ≥ 25 kg). While aerobic dive limits scale with an exponent of 0.6, an analysis of average dive durations in free-ranging chelonian marine turtles revealed that dive duration increases with a mass exponent of 0.51, although there was considerable scatter around the regression line. While this highlights the need to determine more parameters that affect the duration-body mass relationship, our results provide a reference point for calculating oxygen storage capacities and air volumes available for buoyancy control.

Ontogeny of plunge diving behaviour in brown boobies: Application of a data logging technique to hand-raised seabirds

How do seabirds acquire diving skills after fledging? This is an important issue to complete our basic knowledge of life history in seabirds, but the mobility of juveniles obstructs the continuous recording of the development of diving behaviour. In this study, we raised hatchling brown boobies, Sula leucogaster, which are known to have a long post-fledging period. Once boobies began to fly, they made round trips between the sea and the nest, and begged for food from us, their surrogate parents. During this post-fledging care period, the development of diving behaviour was recorded using data loggers. In addition, we attached data loggers to adult brown boobies in the field and compared their diving performance with that of juveniles. The hand-raised juveniles had relatively slow development of diving ability during the first month after fledging. This slow development of behaviour with ontogeny might be the proximate cause for the extended post-fledging care period in this species. This study shows that the combination of bio-logging and hand raising of seabirds is a useful tool for assessing the ontogeny of diving behaviour in these animals.

Parameter Determination for a Computer Simulation Model of a Diver and a Springboard

This study used kinematic data on springboard diving performances to estimate viscoelastic parameters of a planar model of a springboard and diver with wobbling masses in the trunk, thigh, and calf segments and spring dampers acting at the heel, ball, and toe of the foot segment. A subject-specific angle-driven eight-segment model was used with an optimization algorithm to determine viscoelastic parameter values by matching simulations to four diving performances. Using the parameters determined from the matching of a single dive in a simulation of another dive resulted in up to 31% difference between simulation and performance, indicating the danger of using too small a set of kinematic data. However, using four dives in a combined matching process to obtain a common set of parameters resulted in a mean difference of 8.6%. Because these four dives included very different rotational requirements, it is anticipated that the combined parameter set can be used with other dives from these two groups.

Body cooling and the diving capabilities of muskrats ( Ondatra zibethicus): A test of the adaptive hypothermia hypothesis

We tested the hypothesis that immersion hypothermia enhances the diving capabilities of adult and juvenile muskrats by reducing rates of oxygen consumption (V˙O 2). Declines in abdominal body temperature ( T b) comparable to those observed in nature (0.5–3.5 °C) were induced by pre-chilling animals in 6 °C water. Pre-chilling did not reduce diving V˙O 2 of any animal tested in 10 °C or 30 °C water, irrespective of the nature of the dive. Most behavioural indices of dive performance, including average and cumulative dive times, were unaffected by T b reduction in adults, but depressed in hypothermic juveniles (200–400 g). Hypothermia reduced diving heart rate only on short (< 25 s) dives (16% reduction, P = 0.01), but did not affect the temporal onset of diving bradycardia. Post-immersion V˙O 2 was higher for pre-chilled than for normothermic muskrats, but the difference became insignificant on longer (> 90 s) dives. Our findings suggest that the mild hypothermia experienced by muskrats in nature has minimal effect on diving and post-immersion metabolic costs, and thus has little impact on the dive performance of this northern semi-aquatic mammal.

Ontogeny of dive performance in pup and juvenile Steller sea lions in Alaska

Development of competent diving ability is critical to obtaining nutritional independence in marine mammals such as Steller sea lions (SSLs), Eumetopias jubatus (Schreber, 1776). We studied diving performance in pup (75) and juvenile (36) SSLs using satellite data recorders. In general, dives by SSLs were brief and shallow. Overall, 82.3% of dives were &lt;2 min long and 86.9% of dives were &lt;10 m deep. Long (&gt;5 min) and deep dives (&gt;100 m) constituted only 2.49% and 0.77%, respectively, of total dives. We used linear mixed-effects models to investigate the relationships between the response variables maximum-daily-depth, time-at-depth, mean-dive-duration, dive rate, and time-at-sea and the predictor variables age, sex, population (eastern and western Alaska populations), time-of-day, and month-of-year. All response variables except dive rate were positively related (P &lt; 0.05) to age. Dive rate declined (P &lt; 0.001) with age. Time-of-day, month, population, sex, and some first-order interactions were all significantly (P &lt; 0.05) related to some measure of diving performance. With large samples we were able to identify significant relationships between the response variables and the predictor variables, even though the total amount of variation explained by the models was low, because most dives were short and shallow regardless of age, sex, population, time-of-day, or month-of-year. Depths and durations of dives by juvenile animals increased throughout the range of ages studied and were similar to or greater than those previously reported for juveniles and adult females. We expect maximum depths and durations to continue to increase with age until body mass plateaus at about 10 years of age. Therefore, we expect older animals to be more efficient foragers, as they would have greater aerobic dive limits as well as more experience locating and capturing prey.

Diving Ability of the Madeiran Storm Petrel

Although storm petrels are regarded as surface feeders, there is evidence that some species can dive. However, their diving performances and the importance of diving in their foraging tactics have never been accurately assessed. This study aimed to determine the occurrence of diving behavior and the diving ability of the Madeiran Storm Petrel (Oceanodroma castro) using maximum depth gauges. Out of 29 gauges deployed, 18 were recovered and 16 were readable. All the birds had dived, the maximum depths recorded averaging 0.85 m, and diving is part of the typical foraging behavior of the Madeiran Storm Petrel. This study provides a new insight on storm petrel foraging strategies.

A Cross-cultural Study of Precompetition Anxiety and Performance in Diving

1517 Hanin's (1980) Individual zones of optimal functioning (IZOF) theory contends that for each individual there exist a specific range, or zone, of state anxiety that is most conductive to superior performance. However, comparable information is not available in junior divers. PURPOSE: The intent of this study was to test the efficacy of Hanin's IZOF theory to explain the relationship between precompetition anxiety (PCA) and performance with 22 junior divers having different nationalities (14 Japanese and 8 American). METHODS: Each diver first completed the state version of the SATI (Japanese or English version, Form X-1) utilizing the standard instructional set, and this served as a baseline measure. Then divers performed retrospective recall of past competition modeled after a protocol described by Hanin. This was achieved by having the divers fill out the state version of SATI three separate time on the basis of how they recall feeling immediately before the:(a) best, (b) worst, (c) best of the most difficult dive during their previous season. RESULTS: The result indicated that PCA was significantly greater than baseline for recall of best, worst, best of the most difficult dive performances (P<0.05). In accordance with IZOF theory, considerable variation was found in the range of recalled best PCA (IZOF) and 72.7% of divers reported performing best at either low or high levels of PCA. In the contrast of cultural difference, while Japanese showed significant elevation in PCA for all recalled conditions, American elevated PCA only in the recalled worst condition (P<0.05). In addition, Japanese possessed higher recalled best PCA than that of American's (P<0.05). CONCLUSIONS: These findings support Hanin's Individual Zones of Optimal Functioning Theory despite of the cultural difference. It possibly imply that coaches and divers should maintain their PCA level within their IZOF to perform best rather than merely lowering PCA levels for all divers that is generally used in relaxation technique based on the Inverted-U hypothesis.

First records of oceanic dive profiles for leatherback turtles, Dermochelys coriacea, indicate behavioural plasticity associated with long-distance migration

We used Satellite Relay Data Loggers to obtain the first dive profiles for critically endangered leatherback turtles outside the nesting season. As individuals moved from the Caribbean out into the Atlantic, key aspects of their diving behaviour changed markedly, in line with theoretical predictions for how dive duration should vary with foraging success. In particular, in the Atlantic, where foraging success is expected to be higher, dives became much longer than in the Caribbean. The deepest-ever dive profile recorded for a reptile was obtained in the oceanic Atlantic, with a 54-min dive to 626 m on 26 August 2002. However, dives were typically much shallower (generally <200 m) and shorter (<40 min). These results highlight the suitability of this species for testing models of dive performance.

Penguins predict their performance

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 249:305-310 (2003) - doi:10.3354/meps249305 Penguins predict their performance Rory P. Wilson* Institut für Meereskunde, Düsternbrooker Weg 20, 24105 Kiel, Germany *Email: rwilson@ifm.uni-kiel.de ABSTRACT: New technology has allowed inter-dive oxygen-loading behaviour to be assessed in free-living Magellanic penguins Spheniscus magellanicus and shows, via pre-dive hyperventilation and oxygen loading, that birds predict both their upcoming dive performance in terms of duration and depth, and foraging success based on the number of prey they are likely to catch. Thus wild penguins make decisions based on complex environmental parameters and this leads to particularly efficient time use as expected according to optimized foraging. KEY WORDS: Oxygen loading · Optimal foraging · Predator prey interactions · Magellanic penguin Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 249. Online publication date: March 10, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Body oxygen stores, aerobic dive limits and diving behaviour of the star-nosed mole (Condylura cristata) and comparisons with non-aquatic talpids

The dive performance, oxygen storage capacity and partitioning of body oxygen reserves of one of the world's smallest mammalian divers, the star-nosed mole Condylura cristata, were investigated. On the basis of 722 voluntary dives recorded from 18 captive star-nosed moles, the mean dive duration (9.2+/-0.2 s; mean +/- S.E.M.) and maximum recorded dive time (47 s) of this insectivore were comparable with those of several substantially larger semi-aquatic endotherms. Total body O(2) stores of adult star-nosed moles (34.0 ml kg(-1)) were 16.4 % higher than for similarly sized, strictly fossorial coast moles Scapanus orarius (29.2 ml kg(-1)), with the greatest differences observed in lung and muscle O(2) storage capacity. The mean lung volume of C. cristata (8.09 ml 100 g(-1)) was 1.81 times the predicted allometric value and exceeded that of coast moles by 65.4 % (P=0.0001). The overall mean myoglobin (Mb) concentration of skeletal muscles of adult star-nosed moles (13.57+/-0.40 mg g(-1) wet tissue, N=7) was 19.5 % higher than for coast moles (11.36+/-0.34 mg g(-1) wet tissue, N=10; P=0.0008) and 54.2 % higher than for American shrew-moles Neurotrichus gibbsii (8.8 mg g(-1) wet tissue; N=2). The mean skeletal muscle Mb content of adult star-nosed moles was 91.1 % higher than for juveniles of this species (P<0.0001). On the basis of an average diving metabolic rate of 5.38+/-0.35 ml O(2) g(-1) h(-1) (N=11), the calculated aerobic dive limit (ADL) of star-nosed moles was 22.8 s for adults and 20.7 s for juveniles. Only 2.9 % of voluntary dives by adult and juvenile star-nosed moles exceeded their respective calculated ADLs, suggesting that star-nosed moles rarely exploit anaerobic metabolism while diving, a conclusion supported by the low buffering capacity of their skeletal muscles. We suggest that a high mass-specific O(2) storage capacity and relatively low metabolic cost of submergence are key contributors to the impressive dive performance of these diminutive insectivores.

Body oxygen stores, aerobic dive limits, and the diving abilities of juvenile and adult muskrats (Ondatra zibethicus).

Intraspecific variability in body oxygen reserves, muscle buffering capacity, diving metabolic rate, and diving behavior were examined in recently captured juvenile and adult muskrats. Allometric scaling exponents for lung (b=1.04), blood (b=0.91), and total body oxygen storage capacity (b=1.09) did not differ from unity. The concentration of skeletal muscle myoglobin scaled positively with mass in 254-600-g juveniles (b=1.63) but was mass-independent in larger individuals. Scaling exponents for diving metabolic rate and calculated aerobic dive limit (ADL) were 0.74 and 0.37, respectively. Contrary to allometric predictions, we found no evidence that the diving abilities of muskrats increased with age or body size. Juveniles aged 1-2 mo exhibited similar dive times but dove more frequently than summer-caught adults. Average and cumulative dive times and dive&rcolon;surface ratios were highest for fall- and winter-caught muskrats. Total body oxygen reserves were greatest in winter, mainly due to an increase in blood oxygen storage capacity. The buffering capacity of the hind limb swimming muscles also was highest in winter-caught animals. Several behavioral indicators of dive performance, including average and maximum duration of voluntary dives, varied positively with blood hemoglobin and muscle myoglobin concentration of muskrats. However, none of the behavioral measures were strongly correlated with the total body oxygen reserves or ADLs derived for these same individuals.