BIOL 30 Diffusion & Experimental Design In-Class Problem Set #3 3 SJSU Research Case Study: Shaffer Lab The Shaffer lab studies the ecology of seabirds using biologging devices (i.e. fancy tracking tags) attached to feathers on a bird to understand where, when, and how birds find food across vast ocean seascapes. They also use injectable isotopic water to measure field metabolic rate (CO
2
production), which represent the activity specific metabolism of wild animals (i.e. think cost of resting vs. finding food). When breeding, wandering albatrosses (
Diomedea exulans
) nest on islands but obtain their food at sea, making them central place foragers because they always return to their nest where their partner incubates the egg or broods the young chick. The cost of reproduction for parent albatrosses is anticipated to change when chicks hatch out of their egg because parents switch from foraging only for themselves during the long (60-70 days) incubation phase to foraging for themselves and obtaining enough food for their chick (another 8-9 months). Thus, we might predict that parents will modify their foraging effort and behavior as they transition from caring for an egg to satisfying the growing demands of a young chick
that requires frequent meals of fresh squid, krill, and fish. To address this prediction, we injected albatrosses with isotopic water, collected a blood sample and body mass, then equipped each bird with a tracking device to determine where and for how long they foraged at sea. Upon completion of a foraging trip, albatrosses were recaptured at their nest, another blood sample and body mass collected, tracking device removed, and then birds’ were released at their nests. We conducted this experiment at Crozet Archipelago in the Southern Ocean in 1998 during
the incubation and brooding phases of breeding. Overall, we were able to evaluate foraging cost (FMR) and effort (body mass gain per day), distance traveled, foraging locations and routes, and the duration of each foraging trip. If you want to learn more about these results, you can read the paper “
Foraging effort in relation to the constraints of reproduction in free-ranging albatrosses
,” Shaffer et al., 2003. To learn more about research in the Shaffer lab or to see how to apply to do research in the lab visit, our lab website: https://shapelab.gullworks.org
Hypothesis Our hypothesis is that parent wandering albatrosses work harder to obtain food once eggs hatch into small chicks because food requirements increase as parents transition from feeding only themselves (during incubation) to feeding themselves and a chick (during brooding). Data Figure Legend: Comparisons of time at sea and field metabolic rate (FMR) of foraging Wandering Albatrosses (
Diomedea exulans
) during the incubation and brooding phases of breeding. This is measured in Watts per kilogram. Means (±1 SD) for each stage are presented for both sexes combined because no significant differences were observed in mass-specific FMR or time at sea. Statistical differences are denoted as follows *
P < 0·05, **
P < 0·001. Note that each y-axis represents different variables. 11)
What is the dependent variable? Think carefully about what is shown in each half of the figure. (5 pts) 12)
What is the independent variable? (5 pts)
