One population of humpback whales stays in the Arabian sea year-round. Because upwelling allows for primary production to sustain the food web

• Not all cetaceans migrate between feeding and breeding areas, but the breeding congregations are very common for pinnipeds

• Reasons for migration

  • Cetacean breeding:

    • Right whales

      • Move between calving grounds (fall winter, along SE coast) and feeding areas (cape cod area)

    • Gray whales

      • Move between southern winter feeding grounds and northern summer feeding grounds

  • Pinniped breeding:

    • Finer scale fidelity

      • Females will often return to nearly the exact location they were born to give birth

      • Males return within 55m, and females return within 50 meters.

  • Phocids molting

    • Lose large chunks of fur and skin. To regrow, they push blood to the surface. Due to thermoregulation, it is not ideal to do this in the water so they haul out on the beaches

  • Cetaceans

    • Go to warmer waters to molt

  • Avoidance

    • Predators/disease

      • Thought that humpbacks and gray whales migrate to avoid orcas

        • Gray whales stay close to shore when going north with calves, likely to avoid orcas

      • Arabian sea whales accumulate internal parasites, but other whales that migrate fast between feeding and breeding sites starves their parasites.

    • Thermoregulation

      • Calves have a thin blubber layer so metabolism is really high to maintain body temperature in cold waters. This requires mom to feed them a ton, so it is a higher cost to have calves in cold water (even if they can survive)

      • In terms of destination, temperature of the water seems to be driving (it may not necessarily be what prompts them to leave, but it does determine where they go). 

      • Sirenians

        • Natural springs have year round temp of 72 degrees, so manatees migrate to springs in large numbers

        • Warm water refuges near power plants

        • Often where the water is warmer, the food is more scarce so they are required to fast

Population structure

• Population: Group of interbreeding individuals of same species (same species, same place, same time)

  • But there can be two separate populations that overlap in space and time, but do not interbreed

  • St Johns dolphins example. Dolphins north of dry dock will not mate with SJR dolphins (genetic data supports this)

• How do you define the boundaries?

  • Biological

    • Using measurable criteria that are measurable and meaningful to the animals themselves (behavioral and genetic data)

  • Political

    • State or national boundaries. Arbitrary lines humans have created. We often do this to manage stocks, but not often useful

      • Common bottlenose dolphins along east coast

    • Doesn’t make sense in a lot of cases (eg right whales move between canada and u.s)

  • Practical

    • Manageable from a conservation perspective (ie. NOAA fisheries)

      • Set boundaries on a small enough scale that they can manage them

• Population size: Why count?

  • Abundance: Can tell us if there Are

  • enough animals to sustain the population through time

  • Trends: Is the abundance count stable or is in changing? (Can help point to potential threats to the population that can be fixed)

  • Life history characteristics: Survival, growth, reproduction. Number of animals born each season is important to know if population is stable

    • In East Australia, population is super low so the female whales have higher reproductive rate than the pacific coast population.

  • Management success

    • Hawaii closed certain bays from 9:00am-3:00pm to allow spinner dolphins to rest. Community is super mad. So measuring reproductive rate to be sure that this is worth it, is important to maintain that management method.

• Methods for determining abundance

  • Census: Complete count of individuals

    • Not possible for fully aquatic species

    • More possible for species that haul out on beaches via drone images

  • Index counts: Count a sample of individuals that pass through a specific area. 

    • Problematic because some individuals may not pass through the area the same way or at the same time. You can collect trend data, but cannot estimate how many animals are within a population

  • Estimates: Count sample and extrapolate to population

    • Line transects (distance sampling)

      • Line transects: How you collect the data

      • Distance sampling: How you use that data to estimate population size

      • Survey large area (ship or aircraft)

      • Transect lines systematically placed. Spaced appropriately so you don’t miss any animals.

      • Count # of animals and spatial arrangement around line

        • The angle from the transect line and the distance from the spotter. Then you can calculate how far the animal was from the transect line. These numbers must be very precise in order to be accurate. Helps you come up with a probability of sighting animals at certain distances from the transect line which can help you extrapolate your sample.

      • Assumptions:

        • Sample represents population: All age and sex classes

        • No missed animals on the transect line

          • Difficult to accomplish

          • Must be moving slow enough to be able to spot animals before you move through a transect section

        • Animals do not move prior to detection

        • Data recorded accurately

        • Observations independent (not counting the same animal twice)

    • Mark-recapture

      • Mark individuals, release, and then recapture. Some will be marked others 

Migration: Breeding

• Aggregation often forms during breeding seasons

• Site Fidelity to breeding areas varies

  • Cetaceans

    • most lack specific breeding area

      • Exceptions: Humpback, Gray, and Right Whales

  • Pinnipeds

    • finer scale fidelity

• Most cases

  • Marine biologists use estimates to determine population abundance.

  • Transects need angles from the viewers to the animal seen and the distance the animal is from the ship/plane.

  • Transects are done on a larger scale

Mark recapture

• collect data from known individuals (marked) for smaller scale

• Series of surveys Capture

  • mark then release (N)

• N2

  • come back later and do the same and reward

• How many were captured that were already marked (n2)

• Marking isn’t always physical. Marking for whales is just taking a pic of their tail fluke and keeping that for N2 and M2 data

Mark Recapture Assumptions

• Markes have to be unique

  • be careful to not mark 2 different tail flukes as being one whale

• Markes cannot be lost

  • marking should not easily fall off

    • Marks case add on barnacle marking

• All marks are correctly recorded

  • if marking fades, how can you identify them

• Markings do not affect survival

  • If the board is too scary due to the first encounter, the individual will not

• Equal problem of capture with each sample

  • if seasons affect the density of individuals, then the survey must be done within the same season

• Other Ways of mark-recapture Data

  • The movement patterns

    • where their home is stable or a site of fidelity

    • Can create a profile of individuals Ex.1997 she was sited with a cafe (98 no calf 99, 02 yearly sightings with calf annual breeding.

Population Dynamics

• how and why population change

  • stable, increasing, or decreasing pop

• Demographic parameters:

  • Natality: How many families and how many are reproducing each year?

    • (based on the reproductive potential of females)

  • Mortality: has a negative impact in comparison to birth rate (notality)

  • Immigration (+) or Emmigration (-): smaller effects on pop size

  • -N=(B-D)+(I-E)

    • N= pop size

Population Growth: Exp vs. Logistic

• Exp growth

  • \Intrinsic growth rate (r.): maximum potential to increase population size without any negative effects from the environment.

    • predators, limited food, humans, etc.

• How does it change in a given time dN/dt or N

  • Logistic growth: At first growth seen exp. because they have lots of food. As the population grows, resources (food, space) become scarce. Meets carrying capacity (k) (max # of individuals).

• dN/dt = rN (k-N)/k

• * Eventually levels out

• *Don’t need to know equations, must know which is which and if given equation, can you tell if Exp or Logistics

Contains species are able to reproduce a bunch (r.) While other species are limited in reproduction (k)

• Most marine mammals are k species

• Marine mammals take a long time to reach sexual maturity, care for babies for a long time have long lives, and are stable at carrying cap (k).

  • k-species age of sexual maturity takes a while and the mother usually takes care of them during this time.

Density dependence

• Fluctuations around carrying cap., this has effects on future strategies.

  • increase in juvenile mortality: most with nerable / elep ent

    • less experience, smaller body, size, first to experience stress with population size changes

  • increase in age of sexual maturation: If population size exceeds K, mothers ween earlier, can increase risk juvenile success

  • decrease in fertility: no resources, no new birth

    • Females are not physically prepared for pregnancy

  • Increase in adult maturity: if resources are still limited, older and sicker individuals will die

Life history Characteristics

• Nutrition comes first in maintaining the body (brain, muscle, etc)

  • Extra nutrients go to growing the body. If growth is ideal, reproduction will be a priority.

  • A larger body size will have (see slide 10)

    • whale

• Reproductive life history traits (see slide 10)

  • Polar bears are the only exception to the rule of having only one offspring at a time

  • IBI: inter-birth intervals: gestation and IBI will be similar if giving birth and becoming pregnant are close in time.

  • Reproductive lifespan: most mammals reproduce until death. Some species have menopause and continue living long after.

  • Menopause mammals: Resident orcas, Belugas, Narwhals, short-finned pilot whales.

  • Senescence: As you mature, reproductive success decreases

  • Remember: Belugas and Narwhals are close relatives (share common ancestor)

• One population of humpback whales that stay in the Ararbian sea? year round. Because upwelling allows for primary production to sustain the food web

• Not all cetaceans migrate between feeding and breeding areas, but the breeding congregations are very common for pinnipeds

• Reasons for migration

  • Cetacean breeding:

    • Right whales

      • Move between calving grounds (fall winter, along SE coast) and feeding areas (cape cod area)

    • Gray whales

      • Move between southern winter breeding grounds and northern summer feeding grounds

  • Pinniped breeding:

    • Finer scale fidelity

      • Females will often return to nearly the exact location they were born to give birth

      • Males return within 55m, and females return within 50 meters.

  • Phocids molting

    • Lose large chunks of fur and skin. To regrow, they push blood to the surface. Due to thermoregulation, it is not ideal to do this in the water so they haul out on the beaches

  • Cetaceans

    • Go to warmer waters to molt

  • Avoidance

    • Predators/disease

      • Thought that humpbacks and gray whales migrate to avoid orcas

        • Gray whales stay close to shore when going north with calves, likely to avoid orcas

      • Arabian sea whales accumulate internal parasites, but other whales that migrate fast between feeding and breeding sites starves their parasites.

    • Thermoregulation

      • Calves have a thin blubber layer so metabolism is really high to maintain body temperature in cold waters. This requires mom to feed them a ton, so it is a higher cost to have calves in cold water (even if they can survive)

      • In terms of destination, temperature of the water seems to be driving (it may not necessarily be what prompts them to leave, but it does determine where they go). 

      • Sirenians

        • Natural springs have year round temp of 72 degrees, so manatees migrate to springs in large numbers

        • Warm water refuges near power plants

        • Often where the water is warmer, the food is more scarce so they are required to fast

Population structure

• Population: Group of interbreeding individuals of same species (same species, same place, same time)

  • But there can be two separate populations that overlap in space and time, but do not interbreed

  • St Johns dolphins example. Dolphins north of dry dock will not mate with SJR dolphins (genetic data supports this)

• How do you define the boundaries?

  • Biological

    • Using measurable criteria that are measurable and meaningful to the animals themselves (behavioral and genetic data)

  • Political

    • State or national boundaries. Arbitrary lines humans have created. We often do this to manage stocks, but not often useful

      • Common bottlenose dolphins along east coast

    • Doesn’t make sense in a lot of cases (eg right whales move between canada and u.s)

  • Practical

    • Manageable from a conservation perspective (ie. NOAA fisheries)

      • Set boundaries on a small enough scale that they can manage them

• Population size: Why count?

  • Abundance: Can tell us if there Are enough animals to sustain the population through time

  • Trends: Is the abundance count stable or is in changing? (Can help point to potential threats to the population that can be fixed)

  • Life history characteristics: Survival, growth, reproduction. Number of animals born each season is important to know if population is stable

    • In East Australia, population is super low so the female whales have higher reproductive rate than the pacific coast population.

  • Management success

    • Hawaii closed certain bays from 9:00am-3:00pm to allow spinner dolphins to rest. Community is super mad. So measuring reproductive rate to be sure that this is worth it, is important to maintain that management method.

• Methods for determining abundance

  • Census: Complete count of individuals

    • Not possible for fully aquatic species

    • More possible for species that haul out on beaches via drone images

  • Index counts: Count a sample of individuals that pass through a specific area. 

    • Problematic because some individuals may not pass through the area the same way or at the same time. You can collect trend data, but cannot estimate how many animals are within a population

  • Estimates: Count sample and extrapolate to population

    • Line transects (distance sampling)

      • Line transects: How you collect the data

      • Distance sampling: How you use that data to estimate population size

      • Survey large area (ship or aircraft)

      • Transect lines systematically placed. Spaced appropriately so you don’t miss any animals.

      • Count # of animals and spatial arrangement around line

        • The angle from the transect line and the distance from the spotter. Then you can calculate how far the animal was from the transect line. These numbers must be very precise in order to be accurate. Helps you come up with a probability of sighting animals at certain distances from the transect line which can help you extrapolate your sample.

      • Assumptions:

        • Sample represents population: All age and sex classes

        • No missed animals on the transect line

          • Difficult to accomplish

          • Must be moving slow enough to be able to spot animals before you move through a transect section

        • Animals do not move prior to detection

        • Data recorded accurately

        • Observations independent (not counting the same animal twice)

    • Mark-recapture

      • Mark individuals, release, and then recapture. Some will be marked others