9: Marine Mammal Behavior and Population Census
- Page ID
- 164667
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If ecology is the study of organisms and their environment, then the study of animal behavior can be thought of as how and why animals interact with their environment. This can be with conspecifics (others of their own species), with other species, or with the physical environment. By studying animals and their behaviors, we can learn about the relationships between animals, the physiological processes that determine their behavior, and perhaps the ultimate reasons for their evolutionary success. Niko Tinbergen, one of the fathers of ethology, stated that we should pay attention to four kinds of explanations in any instance of behavior: 1. Causation: what are the stimuli that elicit a response, and how has it been modified by recent learning? 2. Development: How does the behavior change with age, and what early experiences are necessary for the behavior to be shown? 3. Evolutionary History: How does the behavior compare with similar behavior in related species, and how might it have arisen? 4. Function: How does the behavior impact the animal's chances of survival and reproduction?
To understand behaviors and the (potential) meanings behind them, the first step is to have a compilation and inventory of the behavior performed by animals of the same species under investigation. This inventory of behavior is an ethogram. Behaviors can be divided into several broad categories, such as courtship, sleeping, aggression, feeding, etc. Each of these broad categories would then likely be reduced to more specific behaviors. This ethogram is the starting point for asking Tinbergen’s questions.
We are all familiar with watching animals every day (especially our own species). Observing behavior is more than just watching; it involves the systematic recording of the activities of the animal, often with particular questions in mind. One issue we need to be careful with is the quality of the data generated from this type of observational study. Interobserver reliability is the agreement between the data recorded by two or more people on the same animal(s). In other words, observation can be somewhat subjective, and two people might ‘see’ different things, or interpret them differently. Another issue we should be conscious of is the temporal limitations (timing) of our observations. How long would it take to generate a complete ethogram of an animal? Would you expect to see all the behaviors of an animal in 30 minutes? What about during day vs. night, during a season, or a year, or a lifetime? What would aliens learn about you if they observed you from 3-5 am, as opposed to 3-5 pm?
Activities
Part 1. Ethogram and Behavior
At the US Coast Guard pier in Monterey, we will observe the behaviors of a large marine mammal, the California Sea Lion (Zalophus californianus). California sea lion lives mainly around the waters of California. It also lives around Oregon, Washington, and British Columbia to the north and Mexico and the Galápagos Islands to the south. Adult male California sea lions measure up to 8 feet in length and weigh an average of 800 pounds, while adult females measure an average of five feet in length and weigh 200 pounds. At around five years of age, males develop a bony bump on top of their skull called a sagittal crest as they reach sexual maturity, and it is this that gives the animal its generic name (loph = "crest"). Females are lighter in color than males. California sea lions are opportunistic eaters, feeding on squid, octopus, herring, rockfish, mackerel, and small sharks. In turn, sea lions are preyed upon by Orcas (killer whales) and great white sharks. They are a highly social species that often occur in large groups and breed around May to June. Most pups are born in June or July and weigh 13-20 lbs. (6-9 kg). They nurse for at least five to six months and sometimes over a year. The males usually leave for feeding grounds during the winter, leaving the females and young pups. Most pups are born in the Channel Islands off Santa Barbara. Most of the small sea lions you see in the Monterey area are already weaned pups or yearlings. CA Sea Lions stay with their mothers for 6-9 months on average. Adult females tend not to migrate as far as the males and primarily stick around Southern CA. During the fall, it would be somewhat rare to see adult females in the Monterey area as they would still have dependent pups at that time of year. It would be safe to say that the majority of the sea lions in the Monterey area during the fall are probably young males.
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Alexdi at English Wikipedia, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons. Rhododendrites, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons. David Merrett from Daventry, England, CC BY 2.0
Sea Lion Ethogram:
- You and a partner will team up and observe the animals for a period of time and then try to formulate a list of behaviors that would create a comprehensive ethogram for the species. How long this will take would depend on what things you are looking for, what assumptions you make, and how active the animals are.
- After you come up with your list, you will then set a specific time frame to observe a single individual or a small group. You could try to keep a running record of behavior, but this is often difficult to do. A more commonly used strategy is to record what an animal is doing at predetermined timed increments, such as every 30 sec, minutes, hours, etc. By keeping track of how often an animal does a particular behavior, you will be able to analyze how the species as a whole spends their time and energy. Since we won’t have much time, this period will need to be short, but it should give you a window into the behavior of the species.
- Both you and your partner will independently record the behaviors of the same animal(s) over the time span of the systematic observation.
Analysis and Write-up: Part 1
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- After the lab, combine your data and generate an average number from the two sets. This will help resolve differences in observer interpretation.
- Construct a graph that shows the amount of time the individuals spent performing the specific behaviors. Hand in this graph and a typed list of your ethogram next week.
- Write one detailed paragraph explaining the methods you used to collect your data.
Part 2. Marine Mammal Population Census
A census is an important process in estimating the population of a species. However, the problems of observing animals for a census are compounded by the fact that most species need to be secretive to survive, either to avoid predation or to be effective predators themselves. They often live in areas that are difficult to access and might be scared away by our approach. There are also important differences in population from season to season or even day to day based on mating, feeding, or other patterns that can shift quickly. They are also often non-randomly distributed because they may favor some specific habitat. Being widely distributed or clumped in groups both offer different challenges for the researcher.
Many methods exist to aid the researcher in their observation, including the use of spotting scopes, binoculars, photographic surveys, infrared and night-vision cameras, aerial counts and photography, pole cameras, balloons and kites with cameras, various marking methods, and statistical analyses that aid in the estimation of a population from a sample observed. Indirect methods can also be used, such as prints, fecal material, fur clumps, etc.
A census works best if it is repeated in a systematic way over time, so you have a long-term data set that can show changes in the population. Since the animals are alive and in the wild, they can be challenging to see and count. They can remain hidden, or move around, and could be erroneously counted more than once. To help with the accuracy of the data, we will average team member data (for the same reasons as above) and also combine the data of all teams into class averages (perhaps others saw something you didn’t).
- Starting at Section A of the Lovers Pt.-Hopkins area (see map), you will partner with another student and survey each of the seven areas (A-G) for marine mammals.
- You will need to:
- Correctly identify target species in the field
- Obtain accurate counts of individuals
- Identify and record the behaviors of the individuals
- Analyze the data after the lab and prepare a census count of the target animals within the survey area.
- You are trying to observe all individuals of the species, so try to find appropriate vantage points from the shore that allow you to see a wide area. Using your binoculars, carefully survey each of the seven areas.
- You will likely need to move to several different locations within each area to adequately cover the whole area.
- Note the locations of kelp beds and other important structures that may influence the animal’s location and activities.
- Note the behavior of the individuals as you perform the survey. You won't be able to spend much time with any one individual, so it will need to be a quick determination. However, when looking back at your data of all the observations, you may find you have noted several different behaviors.
- You will need to:
Analysis and write-up: Part 2
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- Calculate the number of each species observed in each area from your team data.
- Plot your team data for each species (see below).
- Calculate the total population of each species along the entire study area and compare that to your classmates. What is the average?
- Write a one-paragraph figure legend summarizing the methods, results, and conclusion. Imagine giving the graph to someone not in the class- what information would they need to know to understand the figure and its implications?
Graphing hints:
I have recorded a short video showing you how to graph the data from the marine mammal lab and post it on YouTube, or find a link on Canvas. It addresses one of the important problems people often have, which is adding a secondary axis to deal with the drastically unbalanced data from section A compared to the others.
