Number cruncher calculates whether whales are acting weirdly

Date:
July 6, 2023
Source:
University of Copenhagen - Faculty of Science
Summary:
We humans can be a scary acquaintance for whales in the wild. This
includes marine biologists tagging them with measuring devices to
understand them better. These experiences can make whales behave
erratically for a while. Such behaviour can affect research quality
and highlights an animal ethics dilemma. Now, researchers have
figured out how to solve the problems with math.


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FULL STORY ==========================================================================
We humans can be a scary acquaintance for whales in the wild. This
includes marine biologists tagging them with measuring devices to
understand them better. These experiences can make whales behave
erratically for a while. Such behaviour can affect research quality and highlights an animal ethics dilemma.

Now, University of Copenhagen researchers have figured out how to solve
the problems with math.

Maybe you have tried taking a howling pooch or cranky cat to the vet.

Regardless of your noblest intentions, your pet's experience may have
been equally unpleasant. Animals react to the unknown in their own
way. The case is no different for cetaceans like narwhal and bowhead
whales when they encounter human generated noises such as ship noise
or mining blasts in the North Atlantic -- or when they are caught by well-meaning marine biologists who just want to get to know them better.

When biologists 'tag' whales with measuring devices, the animals react
by behaving unusually -- abnormally. For example, for a while after being tagged, they may perform many atypical shallow dives and quick jerks. Such behaviour is misleading when the goal is to study the animal's normal
and natural behaviour.

The problem is getting help from an unusual corner.

"Biologists seek to understand animals as natural beings, but their
reactions turn into unnatural behaviour that creates noise in the
dataset. Because of this, a lot of data from just after whales are
tagged ends up getting discarded. In this study, we have proposed a mathematical approach using statistical methods that can determine
exactly how much data to keep," says PhD student Lars Reiter from the Department of Mathematics.

Valuable for humans and animals alike With two statistical calculations,
the researcher has found a way to estimate when whales like narwhals
and bowhead whales will return to their natural behaviour after being
tagged. It is a method that can also be used to study how animals respond
to other types of disturbances.

"This research is extremely valuable to us as marine biologists who
are interested in the behaviour and well-being of whales. It provides
us with a standardised approach by which to distinguish between
natural behaviour and affected behaviour in whales. Thus far, we've
made individual estimates that are more or less spot on," says marine
biologist Outi Tervo from the Greenland Institute of Natural Resources,
who collaborated with the mathematicians on the study.

The statistical method allows researchers to avoid discarding too much
or too little data. If too much data is kept, it can interfere with the research results, and if too much is lost, it comes at cost to both the
animals and humans.

"It really matters in terms of research, but also financially. And
not least, it means something for animal welfare. If we throw away
data unnecessarily, more whales will eventually have to go through the experience for us to conduct this research, which is ultimately meant
to benefit the animals," says Outi Tervo.

Idea came from a parliamentary election Whale behaviour does not go from abnormal to normal with a flick of its tail.

Their behaviour normalizes gradually, typically over a day -- and in
a few cases over a longer period of time. During this transition, a
whale's behaviour manifests itself on both sides of an area designated
as normal whale behaviour.

So how do scientists figure out where to make the cut? "The idea came
to me while I was standing in the voting booth during parliamentary
elections. Borrowing from the logic of the electoral system, you can
consider it as if the whales -- or these data points which show the
whale's behaviour -- vote on whether they are in or out of their normal
range," explains Lars Reiter.

By recording 1 positive "vote" when the behaviour is within the normal
range, and 1 negative "vote" when outside, the scientists can add up
all the votes and find the moment at which the number of votes goes from predominantly negative to positive.

The researchers use two approaches to determine normal whale behaviour. In part, they look at the whale's diving pattern, as well as its acceleration
and fine motor skills.

How to calculate the behaviour of animals statistically Sometimes it hunts
in the deep, while at others times, it cruises quietly at the surface. The activity that a whale is engaged in is crucial for understanding its
normal energy level. Lars Reiter's method takes this into account as
something new: "Where previous research focused on the mean behavior,
we instead situate a whale in an activity based on its movements --
where it is assessed based on a normal value for acceleration that
matches the speci?c activity being engaged in. We do this by using what
are known as quantiles, instead of averages, because they allow us to
focus on behavioural extremes. For example, hunting and resting are
opposing extremes in terms of energy levels," explains Lars Reiter.

When the focus is on the whale's diving profile, on the other hand,
you look at the pattern formed by the whale's overall activities. By
combining depth and time, one can assess whether the distribution of
different dive types is natural.

Wiser about the animals' hardships and better at avoiding them According
to the marine biologist, the data-based approach represented by the
statistical method also means that researchers can now develop better,
more gentle ways of tagging.

"Based on this study, we already know that the amount of time we spend
putting the equipment on is an important factor for how much the animals
are affected afterwards. Therefore, we can set up some time limits --
where we stop and set the whale free if it takes more than X number of
minutes allowed," says Outi Tervo.

A shift away from individual estimates to a mathematical standard could
also mean better assessments from the veterinary oversight that tag-using research projects are required to go through.

"The method will make it so that ethical approval from a veterinary
inspection is more data-based and precise. So, there is no doubt that this research is a step forward for animal welfare," says the marine biologist.

* Extra info: An important instrument for a future with less ice and
more people The natural Arctic habitat of narwhals and bowhead whales
is changing due to climate change. Annual ice shrinkage and increasing
human activity is taking place in areas that whales once had all to
themselves. The researchers' method can become an important instrument
and contribute to a greater understanding of the consequences.

"It allows us to study how whales are impacted by various human
activities.

They can be external sources of noise that we can situate in time and
location, such as a blast or a ship passing by. Or sounds and activities
that we emit ourselves. Lars' algorithm lets us get a clear picture of
how it all affects the animals," says Outi Tervo.

Increased activity will lead to more ocean noise, which is of concern
to marine biologists with regards to how it will affect large marine
animals like narwhal, which are incredibly sensitive to sound. Co-author
and supervisor Professor Susanne Ditlevsen believes that the studies
and new method will become more important in the years ahead.

"Climate change is leading to increased anthropogenic activity in Arctic
whale habitats. Melting ice means that areas which were once impassable
can now be reached by humans. We would like to assess whether it scares
and disturbs the animals, but it is not clear how. The new methods can
be used to assess at what distance from the animal habitat should various activities take place," says Susanne Ditlevsen.

Facts: Statistical method with two mathematical calculations and one intersection.

The statistical method can generally be understood as calculations with
two types of tagging data -- acceleration and depth, and a way of adding
it up that finds the optimal intersection.

1. Acceleration tells about the energy level and whale movements
("jerks"). The indicators for natural behaviour are divided according
to whale activity, so that, for example, a high energy level is recorded
as natural in connection with hunting, but not in connection with rest.

2. The whale's diving profile is measured in depth and time spent on
a dive.

Temporal impacts over a 40-hour period show a pattern of different types
of dives -- e.g., U-dives, where the whale stay at depth for some time,
or V- dives, where the whale resurfaces quickly. The pattern is compared
with normal values measured after the 40 hours.

3. The cut-off point for when the whale is back in normal behaviour is
found by counting the individual measurements as "voting for or against"
normal behaviour. As such, the researchers find the optimal place to
divide the research data into natural and influenced behaviour.

About the study The study is part of a larger research collaboration
between the Greenland Institute of Natural Resources and the University
of Copenhagen's Department of Mathematics, that focuses on the Arctic's
large marine mammals.

The researchers include Lars Reiter Nielsen and Susanne Ditlevsen from the University of Copenhagen, Outi M. Tervo and Mads Peter Heide-Jo/rgensen
from the Greenland Institute of Natural Resources and Susanna B. Blackwell
from Greeneridge Sciences, Inc., Santa Barbara, USA
* RELATED_TOPICS
o Plants_&_Animals
# Dolphins_and_Whales # Marine_Biology # Animals #
Sea_Life
o Computers_&_Math
# Artificial_Intelligence # Statistics #
Information_Technology # Mathematics
* RELATED_TERMS
o Baleen_whale o Right_whale o Blue_Whale o Sperm_Whale o
Whale o Dog_intelligence o Bowhead_Whale o Whale_song

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========================================================================== Journal Reference:
1. Lars Reiter Nielsen, Outi M. Tervo, Susanna B. Blackwell, Mads Peter
Heide‐Jo/rgensen, Susanne Ditlevsen. Using quantile regression
and relative entropy to assess the period of anomalous behavior
of marine mammals following tagging. Ecology and Evolution, 2023;
13 (4) DOI: 10.1002/ece3.9967 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230706124603.htm

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