Time-depth Recorders Research Articles

Multiple foraging strategies in a marine apex predator, the Galapagos Sea Lion

Three fundamental foraging patterns in air-breathing marine vertebrates have been described: epipelagic, mesopelagic and benthic. Many sea lion species with access to extensive continental shelves have been described as benthic foragers. Coincidently these species are considered threatened. The Galapagos sea lion Zalophus wollebaeki, a top predator in the Galapagos Islands, is also considered threatened in this ecosystem. Sea lions at the central part of the archipelago have access to a vast continental shelf. For this reason we hypothesized that sea lions within this region would dive benthically. In addition, effective protection and conservation of this species requires knowledge of their foraging patterns and habitat utilization. We investigated the diving behaviour and habitat utilization of female Z. wollebaeki of a centrally located colony situated inside the highest density area of the population using time-depth recorders and satellite telemetry. Three distinct foraging patterns were found and described (shallow, deep and bottom divers), and individuals utilizing each pattern foraged in different locations. Epipelagic, mesopelagic and benthic dives were exhibited in the sea lions’ diving behaviour, but these dive types were not exclusively associated with a foraging pattern. Between foraging trips females hauled out more frequently on other islands than they did on their breeding colony. The finding of 3 distinct foraging patterns that differ spatially has direct implications for management, particularly with regard to fisheries interactions. Marine protected areas can be implemented in the regions described as Z. wollebaeki foraging areas. Z. wollebaeki’s wide foraging range coupled with their use of multiple haul-out sites should be considered in future studies when determining foraging trip lengths and habitat utilization since presence/absence from the colony does not reflect foraging trip length

Diving behaviour of jellyfish equipped with electronic tags

Jellyfish are one of the most abundant and conspicuous members of our coastal marine fauna and are now known to play major trophic roles in marine systems. However, little is known about the movements and behaviour of individuals. We equipped individual compass jellyfish (Chrysaora hysoscella) (n = 15) off the Dingle coast, Ireland, with miniature time-depth recorders to log their depth over periods of a few hours. Vertical movements were extensive, with all jellyfish changing their depth during tracking. A range of vertical movements were seen including initial diving from the surface down to a maximum of 29.6 m after device attachment, some jellyfish remaining near the bottom, some moving up and down in mid-water and some moving back near the surface. These results show that jellyfish actively reposition themselves in the water column over small time-scales and open the way for more extensive studies equipping jellyfish with electronic tags.

Animal-Borne Instrumentation Systems and the Animals that Bear Them: Then (1939) and Now (2007)

The history of animal-borne instrumentation is reviewed from the first basic depth gauge invented in the late 1800s, to the complex animal-borne imagery and archival systems of the present day. A major breakthrough occurred in 1964 when the first time-depth recorder was deployed on a Weddell Seal in McMurdo Sound, Antarctica. The next phase in the study of animals at sea was the use of microprocessors as archival recorders in the mid-1980s. These also were first attached to Weddell seals in McMurdo Sound. Microprocessor technology made possible the next major step of attaching a video camera housed in a submersible case (Crittercam) to a loggerhead turtle. Since the 1990s the field of “Biologging” has flourished, with new additions of satellite and GPS tracking, and resulted in three major international symposiums in the past four years (2003-2007).

Foraging behaviour and energetics of Cape gannets Morus capensis feeding on live prey and fishery discards in the Benguela upwelling system

We compared the foraging ecology of Cape gannets Morus capensis attending 2 colonies of equivalent size, yet with contrasting diet and population trends. One colony, on the west coast of South Africa, is decreasing in size and its occupants feed mainly on fishery wastes, whereas the other colony, on the south coast of South Africa, is growing and its occupants feed exclusively on natural prey (pelagic fish). In October and November 2005, we examined the diet, at-sea behaviour, and energy requirements of breeding gannets using direct observations, miniaturised GPS loggers, and time-depth recorders attached to foraging adults. Concurrent hydroacoustic surveys allowed us to assess the distribution and abundance of their preferred prey (the sardine Sardinops sagax and anchovy Engraulis encrasicolus). Birds from the declining west coast colony foraged in areas contain- ing very low abundances of pelagic fish. They fed primarily on low-energy fishery discards. They increased their foraging effort and exploited a greater area than birds from the growing colony, which took advantage of abundant pelagic fish stocks in their foraging range. A marked eastward shift of pelagic fish initiated in the late 1990s has resulted in the shortage of natural prey to Cape gannets on the west coast, strongly suggesting that the local population trend is driven by food avail- ability during the breeding season. A bioenergetic model showed that enhanced availability of low- energy fishery discards does not seem to compensate for the absence of natural prey. Added to the predation pressure by the Cape fur seal Arctocephalus pusillus and the great white pelican Pelecanus onocrotalus, those threats weigh heavily on a vulnerable seabird population.

Development of foraging behavior in juvenile northern elephant seals

AbstractRapid development of foraging ability is critical for phocids. In northern elephant seals Mirounga angustirostris, juvenile survivorship is low compared with adults and foraging difficulties are potentially associated with increased mortality. At Año Nuevo, California, foraging behavior of nine juvenile females during their third foraging migration and five juvenile females on their fourth foraging migration were documented using a variety of commercially available and custom time depth recorders. Foraging success, diving ability, time at depth, bouts of behavior and body composition changes were compared between trips to sea. There were no significant differences in foraging success measured as mass gain between the third and fourth trips to sea. There were differences in how energy was deposited between lean and adipose tissue compartments. Diving ability developed between trips to sea, reflected in significant increases in depth, dive duration and bottom time. Development also occurred within trips to sea. Depth, dive duration and bottom time increased with time at sea. Aerobic capacity appears to increase between the third and fourth trip, with a significantly increased percentage of total time submerged and a significantly lower diving rate. All juveniles on the fourth trip and four out of nine juveniles on the third trip followed marked diel patterns, foraging deep during the day and shallow at night. Like adults, juveniles appeared to stay primarily aerobic with surface intervals independent of dive durations. These results confirm that female juvenile northern elephant seals undergo important developmental changes in foraging behavior between the third and fourth trip, but these changes do not significantly impact foraging success.

Increasing abundance of bowhead whales in West Greenland

In April 2006, a dedicated survey of bowhead whales (Balaena mysticetus) was conducted on the former whaling ground in West Greenland to determine the current wintering population abundance. This effort included a double platform aerial survey design, satellite tracking of the movements of nine whales, and estimation of high-resolution surface time from 14 whales instrumented with time-depth recorders. Bowhead whales were estimated to spend an average of 24% (cv=0.03) of the time at or above 2m depth, the maximum depth at which they can be seen on the trackline. This resulted in a fully corrected abundance estimate of 1229 (95% CI: 495-2939) bowhead whales when the availability factor was applied and sightings missed by observers were corrected. This surprisingly large population estimate is puzzling given that the change in abundance cannot be explained by a recent or rapid growth in population size. One possible explanation is that the population, which demonstrates high age and sex segregation, has recently attained a certain threshold size elsewhere, and a higher abundance of mature females appears on the winter and spring feeding ground in West Greenland. This in combination with the latest severe reduction in sea ice facilitating access to coastal areas might explain the surprising increase in bowhead whale abundance in West Greenland.

Consistent foraging routes and benthic foraging behaviour in yellow-eyed penguins

Yellow-eyed penguins Megadyptes antipodes seemingly forage at discrete marine loca- tions over the continental shelf, where they are believed to feed predominantly at the seafloor. Such behaviour would distinguish them from most other penguin species that generally employ pelagic foraging strategies. From 2003 to 2005 we studied the foraging behaviour of yellow-eyed penguins breeding near Oamaru, New Zealand. We used 2 types of data loggers: GPS loggers recorded geo- graphical position and dive depth at set intervals, while time-depth recorders (TDRs) recorded only dive depth. The penguins performed day trips (range: 12 to 20 km from the coast) or shorter evening trips (range: <7 km). Consecutive foraging trips of individuals revealed remarkably consistent forag- ing routes. Birds travelled along similar — at times congruent — paths, markedly changed course at distinct locations, and revisited certain locations on separate trips, indicating skilful navigation. Three trip stages could be distinguished on one-day trips. During the outgoing (seaward travelling) and incoming (shoreward travelling) stages the birds followed linear courses. These stages were sep- arated by a period of midday activity in which birds exhibited higher dive effort and often tended to stay within confined areas. The diving behaviour revealed an exclusive bottom-foraging strategy, with 87% of all dives being benthic dives; the majority of non-benthic dives occurred during the last 2 to 3 h of the trip, indicating primarily travelling behaviour. Furthermore, yellow-eyed penguins employ benthic dives not only when feeding but also frequently when travelling. We suggest that benthic dives might facilitate navigation and, consequently, account for the consistent foraging patterns of yellow-eyed penguins.

Activity Budgets Derived From Time‐Depth Recorders in a Diving Mammal

Abstract: We describe a method to convert continuously collected time‐depth data from archival time‐depth recorders (TDRs) into activity budgets for a benthic‐foraging marine mammal. We used data from 14 TDRs to estimate activity‐specific time budgets in sea otters (Enhydra lutris) residing near Cross Sound, southeast Alaska, USA. From the TDRs we constructed a continuous record of behavior for each individual over 39‐46 days during summer of 1999. Behaviors were classified as foraging (diving to the bottom), other diving (traveling, grooming, interacting), and nondiving (assumed resting). The overall average activity budget (proportion of 24‐hr/d) was 0.37 foraging (8.9 hr/d), 0.11 in other diving (2.6 hr/d), and 0.52 nondiving time (12.5 hr/d). We detected significant differences in activity budgets among individuals and between groups within our sample. Historically, the sea otter population in our study area had been expanding and sequentially reoccupying vacant habitat since their reintroduction to the area in the 1960s, and our study animals resided in 2 adjacent yet distinct locations. Males (n = 5) and individuals residing in recently occupied habitat (n = 4) spent 0.28‐0.30 of their time foraging (6.7‐7.2 hr/d), 0.17‐0.18 of their time in other diving behaviors (4.1‐4.3 hr/d), and 0.53‐0.54 of their time resting (12.7‐13.0 hr/d). In contrast, females (n = 9) and individuals residing in longer occupied habitat (n = 10) spent 0.40 of their time foraging (9.6 hr/d), 0.08‐0.09 of their time in other diving behaviors (1.9‐2.2 hr/d), and 0.51‐0.52 of their time resting (12.2‐12.5 hr/d). Consistent with these differences, sea otters residing in more recently occupied habitat captured more and larger clams (Saxidomus spp., Protothaca spp., Macoma spp., Mya spp., Clinocardium spp.) and other prey, and intertidal clams were more abundant and larger in this area. We found that TDRs provided data useful for measuring activity time budgets and behavior patterns in a diving mammal over long and continuous time periods. Fortuitous contrasts in time budgets between areas where our study animals resided suggest that activity time budgets estimated from TDRs may be a sensitive indicator of population status, particularly in relation to prey availability.

Diving behaviour of African penguins: do they differ from other Spheniscus penguins?

African penguins Spheniscus demersus closely resemble Magellanic S. magellanicus and Humboldt S. humboldti penguins and have similar breeding and feeding ecologies. Adults feed on pelagic schooling fish in continental shelf waters, but African penguins have been reported to have shallower dive angles and remain submerged longer for dives to a given depth than their congeners. The few data for African penguins were gathered using relatively large time-depth recorders. We measured diving behaviour of 36 African penguins provisioning small chicks at three colonies near Cape Town, South Africa. Maximum and mean dive depths were 69m and 14m respectively. Diving took place mainly during the day. Although dive depths differed between colonies, there were no significant differences in dive duration or maximum, median or mean depth. Total dive duration, descent time, bottom time, ascent time and dive angle all were strongly correlated with the maximum depth attained. The diving behaviour of African penguins is similar to that of its congeners. Diving performance probably was compromised by the data-logger used in the previous study. Comparative data from Humboldt penguins also indicate potential biases in an earlier study of this species. Care is needed when comparing the diving performance of penguins measured using different loggers.

Deep divers in shallow seas: Southern elephant seals on the Patagonian shelf

Elephant seals are wide-ranging, pelagic, deep-diving (average of 400–600 m) predators that typically travel to open waters and continental shelf edges thousands of kilometers from their land breeding colonies. We report a less common pattern of foraging in the shallow waters of a continental shelf. Southern elephant seals, Mirounga leonina, that breed at Península Valdés (Argentina), face an extended (∼1,000,000 km 2; 400–700 km-wide, depending on track), shallow (<150 m) and seasonally productive plateau, the Patagonian shelf. Adults of both sexes usually cross it in rapid transit to other potential foraging grounds on the shelf edge or in the Argentine Basin, but 2–4 year-old juveniles spread over the plateau and spent months in shallow waters. This behavior was recorded for 9 seals (5 males and 4 females) of 23 satellite-tracked juveniles (springs of 2004 and 2005) and for 2 subadult males studied in previous seasons. Trips included travel trajectories and time spent in areas where swim speed decreased, suggesting foraging. Preferred locations of juvenile females were in the proximity of the shelf break, where stratified waters had relatively high phytoplankton concentrations, but young and subadult males used the relatively cold (7–8 °C), low-salinity (∼33.3) mid-shelf waters, with depths of 105–120 m and a poorly stratified water column. Three of the latter seals, instrumented with time–depth recorders, showed dives compatible with benthic feeding and no diel pattern of depths distribution. Regions of the mid-shelf were used in different seasons and were associated with low chlorophyll- a concentration at the time of the visit, suggesting that surface productivity does not overlap with putative quality habitat for benthic foragers. Benthic diving on the shallow mid-shelf would be a resource partitioning strategy advantageous for young males prior to greater energetic demands of a high growth rate and a large body size. Later in life, the more predictable, bathymetry-forced, shelf-break front may offer the food resources that explain the uninterrupted increase of this population over several decades.

Dispersal and dive patterns in gravid leatherback turtles during the nesting season in French Guiana

We present the first combined analysis of diving behaviour and dispersal data collected from gravid leatherback turtles during 3 consecutive nesting seasons in French Guiana. In total, 23 turtles were fitted with Argos satellite transmitters and 16 individuals (including 6 that were concur- rently satellite-tracked) were equipped with an electronic time-depth recorder for single inter- nesting intervals, i.e. between 2 consecutive ovi-positions. The leatherbacks dispersed over the con- tinental shelf—from the coastal zone to the shelf break—and moved over 546.2 ± 154.1 km (mean ± SD) in waters of French Guiana and neighbouring Suriname. They mostly performed shallow (9.4 ± 9.2 m) and short (4.4 ± 3.4 min) dives with a slight diurnal pattern. They dived deeper as they moved away from the coast, suggesting that they were predominantly following the seabed. Inter-nesting intervals could be divided into 2 phases: the first comprised 75% of the time turtles spent at sea, dur- ing which they dived on average 47 min h -1 , while the second was characterised by lower and more variable diving effort as the turtles returned to shore. The extended movements of leatherbacks and the fine analysis of dive shapes suggest that, in French Guiana, leatherbacks may feed during the inter-nesting interval, probably to compensate for the energy costs associated with reproduction. Consequently, this critically endangered species is exposed to a high risk of interaction with local fisheries over the continental shelf.

Novel GPS tracking of sea turtles as a tool for conservation management

We used recently developed, low-powered, TrackTag™ GPS loggers to track the movements of female loggerhead sea turtles ( Caretta caretta) at the largest breeding population in the Mediterranean (Zakynthos, Greece). Three turtles were tracked for a total of 73 days in May and June 2006, during which time 3753 GPS locations were obtained after filtering outliers (51 per day per turtle). The diving behaviour of these three turtles and three others was also monitored using time–depth recorders (TDR). The GPS data revealed that all three turtles spent most of their time in shallow water (< 4 m sea bed depth) very close to the shore (< 200 m), primarily ranging along an 18.5 km section of coastline. These observations were corroborated by TDR data acquired from all six turtles and frequent first-hand sightings of turtles close to shore during the breeding period. Comparison with random crawl movement models indicated that two of the tracked turtles moved with a similar non-random pattern, suggesting common biophysical processes might be driving their movements. The movement and depth data that we collected both suggest that existing legislation to safeguard sea turtles within this protected region may not include the most critical habitats for female loggerhead sea turtles during the breeding period. Our study demonstrated the feasibility of using GPS tracking to investigate fine-scale movements of a marine vertebrate, illustrating the value of GPS tracking for wildlife conservation management.

Acoustic backscatter from a diving dolphin

The acoustic backscatter of a diving Atlantic bottlenose dolphin (Tursiops truncatus) was measured using Simrad EK-60 echosounders operating at 70, 120, and 200 kHz. The animal was trained to dive to a small platform suspended with a nylon rope from a small boat to various depths, with the maximum depth being 100 m. When the dolphin reached the platform, it was required to station on a bite plate attached to the platform until an acoustic signal was sent to release the animal. A video camera on the platform with the signal sent up on a separate line was used to monitor the animal on the bite plate. A time-depth recorder was also attached to the dolphin to determine the average rate of decent and ascent. Echosounding records were collected while the dolphin descended to and ascended from the platform. A total of 15 echosounding records with the dolphin swimming within the beam of the transducers were collected. Preliminary analysis of the data indicated that target strength varied from about −26 dB to −40 dB with a slight frequency dependency. The echoes from the dolphin were structured with the maximum echoes originating from the vicinity of the lungs.

A thorough and quantified method for classifying seabird diving behaviour

Time-depth recorders are commonly deployed on diving animals to obtain information on their aquatic behaviour. The recorded data provide a 2D profile of diving activity. As analyses of diving behaviour from such profiles have become more complex, these analyses have often suffered from a lack of consistency and rigour. There is a growing need for a simple, comparative method to classify diving behaviour thoroughly and quantitatively. Here, a new approach to the classification of the dive profiles of penguins is described, which probably has applicability for many other diving predators as well. This simple approach uses a small, coherent set of criteria to classify behaviours in a detailed and quantified manner, and with relative objectivity. Classification of diving behaviour is possible from the temporal scale of a wiggle within a dive to the scale of a bout of dives. The new method will make comparisons between species easier and clearer because these comparisons will be undertaken within a consistent, more objective framework.

Offshore Bottlenose Dolphins (Tursiops truncatus): Movement and Dive Behavior Near the Bermuda Pedestal

The behavior of offshore bottlenose dolphins (Tursiops truncatus) in deep water and near oceanic islands is not well known. Using satellite-linked, time-depth recorders, we investigated the movements and dive behavior of offshore bottlenose dolphins in the deep waters surrounding the Bermuda Pedestal. Three dolphins were tracked from 5 to 45 days and traveled a mean distance of 28.3 km/day where mean water depth was −1,402.0 m ± 1,120.7 SD. Regular dives during the night (2100–0259 h local time) to depths greater than 450 m (8.9% of total dives), 46.4% of night dives lasting longer than 5 min, and high hematocrit values reveal the deep-diving capabilities of offshore bottlenose dolphins. During the day (0900–1459 h local time), dives tended to be shallow, with 96% of dives within 50 m of the surface, and of short durations, with 52.7% lasting less than 1 min. At dusk (1500–2059 h local time), the number of dives increased (X̄ = 72.4 ± 19.6), indicating a diel dive cycle. The dive patterns of bottlenose dolphins in Bermuda waters correlate with the reported nightly vertical migrations of mesopelagic prey along the steep-sided Bermuda Pedestal.

Chick-rearing Crozet shags (Phalacrocorax melanogenis) display sex-specific foraging behaviour

We compared, for the first time the foraging ecology of both sexes of the blue-eyed Crozet shag (Phalacrocorax melanogenis), using ventrally attached time depth recorders to investigate differences in time-budget and diving behaviour between the sexes during the chick-rearing. Males were the only ones to dive over 55 m. Females dived mostly between 15 and 35 m, a zone poorly used by males. Females foraged mostly in the morning and males in the afternoon. Females also spent one hour longer diving per day compared to males. There were differences in diving strategies and diet, indicating that both sexes targeted essentially the same prey, but of different sizes, males specializing in bigger fish. Although the relationship between sexual dimorphism and diving depth was positive (larger animals diving deeper), evidence suggests that body size (in terms of oxygen storage capacity) is not sufficient to explain so many differences in foraging ecology. Instead, we propose prey size (possibly driven by a limitation of prey handling ability in relation to beak size) could be an essential factor in shaping the male/female behavioural segregation in the Crozet shag; future studies should concentrate on this particular aspect.

Changes in dive profiles as an indicator of feeding success in king and Adélie penguins

Determining when and how deep avian divers feed remains a challenge despite technical advances. Systems that record oesophageal temperature are able to determine rate of prey ingestion with a high level of accuracy but technical problems still remain to be solved. Here we examine the validity of using changes in depth profiles to infer feeding activity in free-ranging penguins, as more accessible proxies of their feeding success. We used oesophageal temperature loggers with fast temperature sensors, deployed in tandem with time-depth recorders, on king and Adelie penguins. In the king penguin, a high correspondence was found between the number of ingestions recorded per dive and the number of wiggles during the bottom and the ascent part of the dives. In the Adelie penguins, which feed on smaller prey, the number of large temperature drops was linearly related to the number of undulations per dive. The analysis of change in depth profiles from high-resolution time-depth recorders can provide key information to enhance the study of feeding rate and foraging success of these predators. Such potential is especially relevant in the context of using Southern marine top predators to study change in availability of marine resources.

The influence of buoyancy and drag on the dive behaviour of an Arctic seabird, the Thick-billed Murre

We used time–depth recorders to investigate the behaviour of free-ranging Thick-billed Murres ( Uria lomvia L., 1758) after attaching positively (n = 9), negatively (n = 10), or neutrally (n = 9) buoyant handicaps and increasing cross-sectional area by 3% (2.8 cm2; n = 8) or 6% (5.6 cm2; n = 6). When buoyancy was altered or drag increased, murres reduced dive depth and duration, suggesting that murres do not manipulate dive depth to obtain neutral buoyancy during the bottom phase. Ascent rate increased as the bird surfaced and mean ascent rate increased for deeper dives, presumably reflecting steeper dive angles and greater buoyancy during deep dives. For short dives (&lt;150 s), preceding surface pauses were better correlated with dive depth and duration than succeeding surface pauses (surface pauses were “anticipatory”), suggesting that murres control inhalation rates based on anticipated dive depth and duration. Murres reduced ascent rate near the surface, possibly to reduce the risk of decompression sickness. Neutrally buoyant recorders attached to the legs had no effect on chick feeding frequencies or adult mass loss, suggesting that this attachment method may have the least effect on the foraging behaviour of alcids.

Individual dietary specialization and dive behaviour in the California sea otter: Using archival time–depth data to detect alternative foraging strategies

Abstract The existence of individual prey specializations has been reported for an ever-growing number of taxa, and has important ramifications for our understanding of predator–prey dynamics. We use the California sea otter population as a case study to validate the use of archival time–depth data to detect and measure differences in foraging behaviour and diet. We collected observational foraging data from radio-tagged sea otters that had been equipped with Mk9 time depth recorders (TDRs, Wildlife Computers, Redmond, WA). After recapturing the study animals and retrieving the TDRs it was possible to compare the two data types, by matching individual dives from the TDR record with observational data and thus examining behavioural correlates of capture success and prey species. Individuals varied with respect to prey selection, aggregating into one of three distinct dietary specializations. A number of TDR-derived parameters, particularly dive depth and post-dive surface interval, differed predictably between specialist types. A combination of six dive parameters was particularly useful for discriminating between specialist types, and when incorporated into a multivariate cluster analysis, these six parameters resulted in classification of 13 adult female sea otters into three clusters that corresponded almost perfectly to the diet-based classification (1 out of 13 animals was misclassified). Thus based solely on quantifiable traits of time–depth data that have been collected over an appropriate period (in this case 1 year per animal), it was possible to assign female sea otters to diet type with >90% accuracy. TDR data can thus be used as a tool to measure the degree of individual specialization in sea otter populations, a conclusion that will likely apply to other diving marine vertebrates as well. Our ultimate goals must be both to understand the causes of individual specialization, and to incorporate such variation into models of population- and community-level food web dynamics.

The effect of instrument attachment on the surface temperature of juvenile grey seals (Halichoerus grypus) as measured by infrared thermography

Previous research has highlighted the importance of minimising hydrodynamic drag from biologging instruments fitted to marine mammals. However, there is a need to investigate other possible impacts of instruments on animals. The aim of this study was to examine the effect of deploying instruments on the surface temperature distribution of grey seals (Halichoerus grypus). Infrared (IR) thermography was used to record the surface temperature of two juveniles that had been fitted with heart rate recorders and mounting straps for the attachment of a time depth recorder. When animals were fully wet and inactive, the surface temperature pattern was unaffected by instruments. However, as animals dried out regions of high temperature were recorded around the edges of attachment sites compared to surrounding fur. This appeared to be due to heat leakage around the sides of instruments and mounting straps that provided an additional layer of insulation. There were no obvious changes in the surface temperature distribution around instruments associated with duration of deployment. This work shows that attachment of relatively small biologging instruments will produce localised effects on heat transfer in air but will not significantly change the total heat exchange of grey seals on land or at sea. IR thermography was also shown to be a useful method of detecting surface temperature patterns associated with epidural anaesthesia and blubber biopsy.