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Introduction

            Cetaceans are known for their complex brains, high
intelligence, and exceptional social structures. They possess traits of
culture, empathy, and self-awareness. Due to these qualities, they are also
susceptible to great amounts of stress and trauma. Stress is a physiological
response from an organism’s body to an environmental threat (Schmitt, 2010). However,
cetaceans possess unique adaptations for living in an aqueous saltwater medium,
such as echolocation, ability to store oxygen, breath-hold dive response, and vascular
rate network that may enhance an animal’s response to a stressor (Schmitt,
2010). Over time, humans have striven to make as much contact with cetaceans as
possible. This included whaling, for meat and other byproducts, capturing young
whales and dolphins to keep as show animals, and increased boat traffic with
the hope to catch a glimpse of the majestic creatures. Because of this,
stresses on cetacean populations were increased. Chronic stress can lead to
loss of fitness and weight loss, reproductive inhibition and social isolation, increased
disease susceptibility, and potentially death (Schmitt, 2010). The most
dramatic response to a stress event is mass mortalities of a population of
animals. Mass mortalities of marine mammals have increased in the last 15-20
years, and there have been many unexplained population declines (Fair, 2000). Cetaceans
are known to have strong social bonds with their pods for life. Some cetaceans
that we still have in captivity today were taken from their pods and transported
to aquariums and theme parks all over the world. They were then placed in small
tanks with members of the same species from completely different areas. In
captivity, there are interspecific interactions, aggressions, trauma,
separations/isolations, illness, procedures that require restraint, and
transport (Schmitt, 2010). All of which these animals must face without the
comfort of their tight social network. However, there is equally as much stress
in the wild for cetaceans. In the wild, cetaceans may experience stress in the
form of noise pollution, predation, interaction with humans and fishery,
climate change, depleted food resources, algal toxins/infectious disease, and other
ecological changes but have impressive social networks that aids in individual
survival and fitness and lessens the weight of environmental stress (Schmitt, 2010).
However, humans will always have a spirit of inquiry when it comes to marine
mammals. Limitations on interactions with wild and captive cetaceans need to
continue to be put in place to conserve the populations.

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Human Interaction Affecting
Captive Cetaceans

          Captive animals are restricted to confined
spaces, so social encounters can become more intense because they may have
limited means of escape. Competition, dominance, and the constant change of
group dynamics can cause great stress on the animals (Waples, 2002). During
instances of stress the body releases larger quantities of ACTH, cortisol, and
aldosterone. ACTH (adrenocorticotropic hormone) is produced and secreted by the
anterior pituitary gland and is produced in response to biological stress.
Cortisol, a response to stress, increases blood sugar and suppresses the immune
system. Aldosterone, a steroid hormone produced in the adrenal gland, is a
regulation of blood pressure. According to a study by Todd L. Schmitt and
others, three captive Beluga whales underwent physical and medical evaluations
where their stress hormes were monitored. They tested these animals hormone
levels at different point throughout the day and drew their conclusions. They evaluated
resting concentrations of ACTH, cortisol, and aldosterone with routine
interaction and medical procedures. ACTH and cortisol were consistently higher
in early morning, while aldosterone was higher in the evening during routine interactions.
All the stress hormones were elevated during physical examination. ACTH
concentrations were most increased, 5–10-fold, during physical examination. Cortisol
and aldosterone showed 2–4-fold elevations. The stress response measured during
the WCS (wading-contact sessions) was not significantly different from baseline
(control) concentrations (Schmitt, 2010).

Stress hormone contraction (¯X ±
SD, n = 15 total, 5 for each beluga).

                         Control (n = 15)

        WCS (n =15)

 

Pre

Post

 

Pre

Post

ACTH
(pg/mL)

10.0±
6.2

6.6±
4.4

 

13.0±
5.7

7.0±
4.9

Cortisol
(mg/dL)

2.1±
0.5

1.5±
0.8

 

1.9±
0.7

1.6±
0.5

Aldosterone(pg/mL)

10.0±
0.00

10.0±
0.00

 

10.0±
0.00

10.0±
0.00

Table 1. Endogenous plasma ACTH was measured
in conjunction with cortisol

and
aldosterone in long-term captive belugas during an unstressed condition vs. that with a modest stressor to evaluate
the changes in multiple stress hormones (Schmitt, 2010).

This serial sampling is needed
to better understand how an individual response over time to stress rather than
using one hormone analyses due to differences in animals hormone production
(Schmitt, 2010). Further studies need to be done to assess what is causing the
stress in the captive animals. Another case study done was done by Kelly Waples
and Nicholas Gales on evaluating and minimizing
social stress in the care of captive bottlenose dolphins. Bottlenose dolphins
are highly social creatures and are susceptible to social stressors. Three
dolphins were the subject of the study, all dolphins were fed appropriately each
day, feed time included training sessions, performances, or occasional free
feeds. The level of dominance was recorded by the trainers based on the number
of rake marks each dolphin received, and interactions with others during
feeding sessions (Waples, 2002). Weight, length, and girth measurements were
recorded monthly and blood samples were collected every 6 months, or more
frequently when health problems arose. During a year, three cases of illness
and mortality occurred within a group of captive bottlenose dolphins held at the
Atlantis Marine Park in Western Australia (Waples, 2002). Social dynamics were observed,
and social stress was targeted to have a great role in their health issues. The
collection of quantitative behavioral data at the time of these health problems
offers a unique opportunity to quantitatively correlate socially related stress
with severe health consequences. Two of the dolphins showed weight loss and gastric
ulceration, as well as lymphopenia, and neutrophilia. All three dolphins stopped
eating, became inactive, and socially isolated, which all show signs of stress.
According to the study, it seemed the stress was caused by changes in the groups
structure as well as aggression from other animals (Waples, 2002). To better
manage captive cetaceans, behavior needs to be more thoroughly monitored to
assess appropriate groupings. With a better established social group,
cetaceans, especially dolphins, have a greater quality of life.   

 

 

 

 

Human
Interaction Affecting Wild Cetaceans

          Most
research on cetacean stress and social interactions is controlled in captivity
such as research labs and marine parks. These environments afford some control,
but they are accompanied by many limitations. These situations impose
tremendous stress on the animals, thus impeding accurate results. However, factors
in the wild also cause considerable stress to these animals as well, entanglement
in lost and discarded fishing gear; ingesting debris, particularly plastics;
habitat degradation; noise and acoustic influences and other human activities
ranging from ship traffic to whale watching; climate change such as rising sea
surface temperatures , chemical pollution, such as industrial chemicals and
pesticides and biological factors, such as, disease, parasites, loss of food
resources, habitat degradation, algal blooms (Fair, 2000). These can cause
immune system disfunction, disruption of communication/ navigation, stranding,
and massive die-offs. Stimuli, such as stress, which is perceived through
the nervous system could affect immunocompetence and the animals ability to
fight off any invaders that may compromise the immune system, and result in
disease or death (Romano, 2002).  There
has been a link identified between the nervous system and the immune system in
the beluga whale, with postganglionic sympathetic nerve fibers innervating
parenchymal lymphoid compartments as well as smooth muscle in primary and
secondary lymphoid organs. The autonomic nervous system is also activated
during stress (Romano, 2002). This means that the more unnecessary stress that
is being caused is hurting cetacean populations. Marine mammals may also be
affected by oil spills, noise, vessel traffic and other environmental stress
associated with oil and gas exploration. Animals within or close to the spill
area will be most affected by inhaling, grooming, or feeding on contaminated
material. Short-term inhalation can irritate mucous tissues, while prolonged
inhalation of high vapor levels would cause death or damage to the nervous
system (Fair 2002). Boat traffic also has a huge affect on stress in cetaceans.
One study found, dolphins spent more time traveling and diving when boats were
present that they did socializing and resting. The time spent socializing was
significantly reduced by almost half, and the time spent resting was
significantly reducing from 11% to 1%(Lusseau, 2003).   

 

Figure
1. Effects of Tour Boats on the Behavior of Bottlenose Dolphins: Using
Markov Chains to Model Anthropogenic (Lusseau, 2003).

It
is difficult to study dolphins in the wild without causing them tremendous
stress. The goal is to obtain an opportunity to work with cetaceans one-on-one,
without causing them social stress. Occasionally, there are individuals known
as lone sociable dolphins, which present the opportunity of doing so (Marino,
2011). Lone sociable dolphins are free-ranging cetacean individuals who are
often solitary, yet, for one reason or another, have initiated, or participated
in, sociable interactions with humans in the wild with some regularity. This
new approach is called Interspecies Collaborative Research (ICR). ICR amounts
to optimizing existing natural conditions for the primary benefit of the
cetacean rather than imposing artificial ones for the sole benefit of the
researcher (Marino, 2011).  This method
also does have great limitations, but it is a less invasive method of
conservation. Human interactions with the environment cause tremendous stresses
to all wild life, especially cetaceans.

Conclusion

Humans greatly impact the environment and cause
stresses to many creatures, including cetaceans. Potential solutions for
cetaceans that are in captivity should include reducing as many stressors as
possible. Monitoring group behaviors and understanding individual association
is the key to improvement. Monitoring social behavior and activity levels will enable
awareness of social problems that may increase social stress on vulnerable
individuals. Creating sanctuaries would be preferable to the stresses of being
confined to artificial tanks. Studies on lone species of cetaceans could
provide vital feedback on how our interactions with cetaceans affect their
welfare. Hopefully, learning more about immunological defense mechanisms in
cetaceans, the impact of environmental factors on the cetacean immune system,
and optimize the health of captive cetaceans while rehabilitating sick or
stranded animals can attribute to conservation. Many populations lack empathy
of their impact or do not know alternative solutions, in addition, to a thirst
for knowledge to obtain information on everything. Continuing to interact with
cetaceans in the way we were was causing problems among populations, hopefully
more steps can be made toward conservation. 

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