Animal Welfare Science – Physiological Measures of Disturbance

In document Impact of Human and Other Disturbance on Behaviour and Heart Rate of Incubating Adélie Penguins (Pygoscelis adeliae) (Page 46-50)


2.3 Human Impact on Animals

2.3.1 Animal Welfare Science Animal Welfare Science – Physiological Measures of Disturbance Animal Welfare Science – Physiological Measures of

Following, characteristics of the parameters potentially relevant to THISSTUDY are briefly described.

As measurements in the hypothalamus (see box 2-4) were clearly out of the question (invasive, requiring immobilisation of animals), characteristics of CRF will not be dwelt upon. Whenever penguin physiology might deviate from that of lab/ farm animals, specific penguin studies are quoted. Any non-referenced statements have been taken from BROOM & JOHNSON (2000).

All physiological parameters (tab. 2-5) used in animal welfare lack context-specificity, that is, changes have been measured in both aversive and pleasurable contexts. With respect to the adrenal axes, for instance, DEBOER & al. stated as early as 199070 that

“[i]t has been clearly established that acute exposure to arousing or stressful stimuli is accompanied by increased sympatho-adreno-medullary and pituitary-adrenocortical activity, resulting in raised plasma concentrations of the catecholamines (CAs), adrenaline (A) and noradrenaline (NA), and of the glucocorticoid corticosterone (CS).”

This fact points to the importance of simultaneous behaviour observations for the interpretation of physiological results, as these help put physiological responses into context (DAWKINS 2003).

Likewise, all parameters are influenced by the animal’s activity as well as by emotions (e.g., pain, fear, fright, aggression, frustration). Therefore, separation of motor from emotional components is paramount regardless of choice of parameter.

Immediacy of response after presentation of a stimulus differs between parameters: It is instant for heart rate and for the adrenal-medullary system (1-2 s), ‘within one minute’ for respiratory rate,

‘within minutes’ for body temperature and ACTH (adrenocorticotropic hormone), and ‘after at least 2 min’ (BROOM & JOHNSON 2000) or 1-2 min (ROMERO & REED 200571) for glucocorticoids. With respect to glucocorticoids, however, earlier authors reported considerably more rapid response times:

Quoting BEUVING & VONDER (1978), SIEGEL (1980) states appearance of glucocorticoids in domestic chickens to start as quickly as 45 s after onset of restraint (= aversive stimulus) followed by a six-fold increase within 8 min.

Delay of waning of response during- or post-stimulus likewise differs among parameters:

While elevated heart rate, respiratory rate, and body temperature have been found to decline more slowly (several minutes to half an hour), adrenaline and noradrenaline (AM) are removed very quickly: BROOM & JOHNSON (2000) quote a half-life in rats of 70 s, while NATELSON & al. (1981) mention 1-3 min for the same species. ACTH is inhibited by glucocorticoids and is quickly removed from the blood so that samples must be taken within a few minutes of the event whose effect is being assessed. In rhesus monkeys, peak ACTH response occurred after 15 min, followed by a steady decline despite pervading conditions afterwards. With respect to glucocorticoids, DEBOER &

al. (1990) showed that in rats, corticosterone levels peaked after 15 min in response to handling and novelty of surroundings, and had dropped to almost pre-measurement levels at the next measuring point half an hour later. In response to water immersion, however, corticosterone levels rose steeply during administration of stimulus, but continued to rise after the stimulus was withdrawn, resulting in even higher levels measured half an hour later 72.

70 italics added in THISSTUDY

71 “These results indicate […] that samples collected in less than 2 min reflect unstressed (baseline) concentrations, and that samples collected from 2-3 min also will likely reflect baseline concentrations but at worst are near baseline [i.e., so near that they may still be used as a baseline for subsequent comparisons].” (ibid. abstract, p. 73)

72 As measuring points were ‘few and far between’, it is not possible to say whether peak responses lay between end of stimulus and 30 min post-stimulus or between 30 min and 75 min post-stimulus.

Pronounced diurnal fluctuations are mentioned for core body temperature, adrenaline and noradrenaline (DEBOER & VAN DER GUGTEN 1987), and HPA. For the latter, the cycle in baseline adrenal cortex activity strongly influences response intensity. CULIK & al. (1989) did not find a clear pattern of periodicity with respect to penguin heart rate. The same study reported susceptibility to climatic conditions for penguin heart rate: Heart rate increased linearly with wind speed but was unrelated to ambient temperature, humidity, cloud cover and estimated solar radiation. Climatic influence has likewise been found for respiratory rate, body temperature, ACTH (increase in cold temperatures – though not in hot, JERONEN & al. 1976), and glucocorticoids (increase in inclement weather, WINGFIELD 1984). As for adrenaline and noradrenaline (AM), susceptibility to ambient temperature was found in, e.g., pigeons (JERONEN & al. 1976).

Given the different target tissues/ organs, methods for obtaining measurements vary in their degree of invasiveness, with observation (respiratory rate) being the least invasive. For penguin heart rate, a variety of apparatus are used, ranging from implants (highly invasive: pre- and post-experimental operations required) and external ECG recorders (highly to moderately invasive:

some ‘tie’ the penguin to the recording box) to artificial eggs (least invasive for HR: pre- and post-experimental approach, but no handling or restriction required). Body temperature in penguins has been measured by implanted devices (necessitating pre- and post-experimental operations) or by taking rectal temperatures (handling for each measurement). Measurements concerning the adrenal axes require blood sampling (AM: intravascular canule, handling and insertion of permanent device; ACTH and glucocorticoids73: handling for each measurement), urine sampling (AM:

catheterisation, handling and insertion of permanent device, results very variable; glucocorticoids:

with considerable delay), faecal sampling (of glucocorticoid metabolites, with considerable delay), or saliva sampling (glucocorticoids: much variation).

Blood samples must be taken within the minimum response time for each parameter to avoid measuring disturbance caused by the procedure itself rather than the disturbance stimulus investigated (BROOM & JOHNSON 2000, ROMERO & REED 2005).

According to COCKREM & al. (2009, p. 158), “capture, followed by the collection of blood samples over 30-60 min is a widely used stressor in studies of corticosterone in birds […]. The increase in plasma corticosterone concentrations whilst birds experience the stressors is termed a corticosterone response […].” The same authors state that, even though corticosterone responses had been found to differ markedly between individuals, variation in corticosterone responses had not been quantified in free-living birds up until 2009.

In situations of stress, the general direction of change for all parameters, (be they cardiac, respiratory, temperature-related or humoral) is ‘up’. One exception to this is found in species exhibiting a ‘freeze’ response (heart rate decrease). Furthermore, peripheral body temperature (but not core body temperature) may decrease.

While respiration rate was initially included as a possible physiological parameter for THIS STUDY, measurements effected by binoculars were soon found too unreliable to include, as focal animals/

groups were located approximately 25-30 m away from the investigator outside visiting experiments, and birds were frequently prone or turned away from the observer.

Of this array of physiological parameters, heart rate was thus considered the most feasible and reliable with respect to suitability for THISSTUDY (unrestrained animals in the field in maritime

73 According to BROOM & JOHNSON (2000), plasma ACTH levels respond earlier than plasma glucocorticoid levels.

Antarctica, hands-off, non-invasive protocol). This decision was much later confirmed by field-related evaluations undertaken by TARLOW & BLUMSTEIN (2006/ 2007).

Table 2-5: Comparison of Selected Characteristics of Physiological Parameters Used in the Assessment of Animal Welfare. Parameters clearly dependent on surgical procedures (e.g., measurement of CRF) have been omitted from the table.

Adrenal Axes:

1. Adrenal-medullary system


Adrenal Axes:

2. Hypothalamic-pituitary-adrenal cortex system (HPA) Parameter/

Attributes of Parameter

Heart Rate Respira-tory Rate


Tempe-rature Catecholamines:



ACTH (Adrenocortico-tropic hormone)

Glucocorticoids (Corticosterone/

Cortisol) in plasma

Context-specific no no no no: 'readying the body for emergency action, both positive and negative'

Activity-related yes yes yes yes

Emotion-related yes yes

yes, e.g., 'protest':




e.g., in humans more passive res-ponse: adrenaline;

more active/ aggres-sive response:



Immediacy of Response after Stimulus Presentation

immediate within 1 min


minutes within 1 s or 2 s

release primarily initi-ated by CRF, also by catecholamines;

appears within minutes (guinea pig: significant increase after 4 min)

release initiated by ACTH;

appears after at least 2 min/

1-2 min

Delay of Disappearance of Response during- or post-Stimulus

may be longer if little behavioural response or much loco-motory activity is shown

longer longer

shorter-lived than HPA;

half-life in rats: 70 s

longer-lived than AM;

release inhibited by glucocorticoids;

removed quickly from blood; rhesus monkey:

peak incr. after 15 min, then decline despite pervading conditions

longer-lived than AM;

peak towards end or even after stimulus administration Pronounced

Diurnal Fluctuation

no (penguins:

CULIK & al.


no core: yes

yes, in conjunction with behavioural

activity (rats)

yes: cycle in baseline adrenal cortex activity

yes: cycle in baseline adrenal cortex activity

Susceptibility to Climatic Conditions

yes (penguins):

increase with wind speed (CULIK & al.



increase with ambient tempe-rature

yes (penguins) increase with ambient temperature (BOYD &



yes: increase in high and low temperatures

yes: increase in low temperatures

yes: e.g.

increase in inclement


Measurements Obtained by

implants, external ECG-recorders, artificial eggs

direct obser-vation

rectal thermo-meter, implanted devices

blood sampling (intravascular canule, immediately after stimulus); urine sampling

(catheterisation, and very variable)

blood sampling (within a few mins)

blood sampling (within 2 min);

urine-sampling (with considera-ble delay); saliva (variable); faecal concentrations of glucocorticoid metabolites (with considerable delay) General

Direction of Change

tachycardia (increase);


species with a 'freeze' response

increase core:



may decrease


Suitability for

THIS STUDY high limited none none

Heart rate measurements in penguins have been employed by a number of studies (also see chapter, Table 3-3 and Table 3-4). As early as 1989, CULIK & al. reported that Adélie penguins exhibited tachycardia (elevated heart rate) in response to human disturbance, especially to being handled (capture and restraint).

Tachycardia is considered a reaction physiologically preparing the animal for the possibility of flight or fight, and the magnitude of the response is often taken to represent an animal’s assessment of the degree of threat to which they are exposed (PRICE & al. 1993). If tachycardia is to be considered a meaningful physiological response to disturbance stimuli, however, care must be taken to distinguish between increases in heart rate due to motor activity and those due to perception of, and reaction to, disturbance, i.e., the ‘emotional response’ (BROOM & JOHNSON 2000). Using a heart rate measuring device which only records heart rate when the penguin is sitting quietly, viz., an artificial egg, serves to separate the former from the latter so that elevations can be attributed to ‘emotional response’ alone. It is acknowledged that it is not permissible to simply extrapolate the (cardiac) reaction of incubating birds to other stages of the breeding cycle (WILSON, R.P. & al.

1991), let alone to the non-breeding period.

To account for individual variation in resting heart rate as well as for susceptibility to climatic conditions, it is recommended that for the assessment of heart rate reactions, each individual serve as their own control (BALDOCK & SIBLY 1990). This is effected by comparing a given individual’s heart rate responses during disturbance to records obtained immediately prior to disturbance (undisturbed/ pre-treatment ‘baseline’) of the same individual.

In THISTHESIS, heart rate was examined (for details see chapter 4) as regards

• extent of tachycardiac (increase) responses during disturbance (human, conspecific),

• overall pattern changes during disturbance (human, conspecific),

• delay until resting levels were reached again,

• extent of fluctuations outside disturbance (‘baseline sessions’),

• parallelity or complementarity with respect to behavioural indicators.

In document Impact of Human and Other Disturbance on Behaviour and Heart Rate of Incubating Adélie Penguins (Pygoscelis adeliae) (Page 46-50)