My research objective is to investigate two spatial aspects of humpback whale (Megaptera novaeangliae) surface feeding in and around the Stellwagen Bank National Marine Sanctuary in the southern Gulf of Maine, USA. Specifically, I aim to:

• Quantify the spatial scale of this behavior.
• Investigate whether this behavior is more frequently observed in certain areas of the study region.

Most studies investigating the spatial scale of humpback whale movement have focused on large spatial and temporal scales, using 1-2 location points per day over the course of several days or weeks during which the animals traveled hundreds or thousands of kilometers (Dalla Rosa et al. 2008; Heide-Jorgensen and Laidre 2007; Kennedy et al. 2013). In contrast, the proposed study aims at investigating the detailed movement of these whales on the temporal and spatial scales of daily bouts of foraging events. Analyzing such fine-scale foraging movement patterns can contribute to our knowledge of how marine predators search for patchily distributed resources (Levin 1992; Pinaud and Weimerskirch 2005).

The existing data for this analysis stems from a long-term study investigating humpback whale behavior and ecology in the southern Gulf of Maine, USA, (for more details, see Friedlaender et al. 2009). Almost every summer since 2004, whales were equipped with non-invasive tags that recorded detailed information on the underwater movement of the whales or collected video-footage of the behavior of the tagged animal and associated whales. During daylight deployments that usually lasted for up to 8 hours, focal follows were conducted from a small boat following the tagged whale, during which detailed information on the behavior of the tagged whale at the water surface was collected. Because the tags did not contain a GPS, range and bearing information on the whale were also collected at least once when the whale was observed at the surface in between consecutive dives, usually resulting in the collection of one location point every 3-5 min. Continuous GPS locations of the boat were automatically collected. Based on the time stamps of the range/bearing data and the boat GPS data, the GPS location collected at or close to the time the range and bearing data was collected, were identified and together this data was used to calculate the location of the whale.

The analysis proposed here will use the whale behavioral observation data to identify focal follows during which surface feeding was observed. The location data of these focal follows will be used for the following analysis. For each focal follow of a surface feeding whale, I will use the R package adehabitat (Calenge 2011) to implement first-passage time analysis to calculate the spatial scale of surface feeding, and to identify areas of intense foraging effort. The following description of the method is based on Fauchald & Tveraa (2003). First-passage time is a metric used to quantify search effort along an animal movement path. Around each location point, a circle of a given radius is created, and the amount of time the animal spent within the area of the circle is measured. The measurement is then repeated for each location point of the animal’s path with successively increasing circle radii. Increasing the radii will increase the amount of time the animal spent within the circle, but the increase in time will be greater in areas of intense search effort compared to areas through which the animal was simply traveling. The radius at which the variance in first-passage time between the different location points is greatest represents the spatial scale of foraging effort. I intend to statistically test for differences in the spatial scales of surface feeding between individuals and as a function of group size. At the radius representing the spatial scale of foraging, those circles with the longest first-passage times identify areas where foraging effort is concentrated (Bailey & Thompson 2006). Comparing the locations of intense foraging effort between individuals, areas within the study region can be identified that represent suitable foraging habitat (Bailey & Thompson 2006). The expected outcome of this part of the analysis is a map of the study region displaying locations of suitable foraging habitat based on first-passage time calculation.

I expect to find that different individuals have a similar spatial scale of surface feeding, as I anticipate that the spatial scale of foraging is correlated with spatial metrics of prey schools (Benoit-Bird et al. 2013). Because the spatial scale of search effort is likely to be larger than the spatial scale of the prey patches themselves, I expect the spatial scale of foraging for all individuals to be larger than the average prey school length in the area, which is ca. 139 m (Hazen et al. 2009). I expect to find a positive correlation between the spatial scale of surface feeding and group size because I anticipate that larger groups will cover a wider area during their search. I expect to see a concentration of surface feeding locations in the western part of the sanctuary region as this has been found to be an important feeding area in a previous study using a subset of the data I am planning on analyzing here (Hazen et al. 2009). This is due to the substrate type, topography and oceanographic conditions in this area which serve to attract and aggregate prey (Hazen et al. 2009).

I currently have basic knowledge of ArcMap and R and no experience with Python or Modelbuilder.

Literature cited:

Bailey, H. & P. Thompson. 2006. “Quantitative Analysis of Bottlenose Dolphin Movement Patterns and Their Relationship with Foraging: Movement Patterns and Foraging.” Journal of Animal Ecology 75 (2): 456–65. doi:10.1111/j.1365-2656.2006.01066.x.

Benoit-Bird, K.J., B.C. Battaile, C.A. Nordstrom, and A.W. Trites. 2013. “Foraging Behavior of Northern Fur Seals Closely Matches the Hierarchical Patch Scales of Prey.” Marine Ecology Progress Series 479 (April): 283–302. doi:10.3354/meps10209.

Calenge, C. 2011. “Analysis of Animal Movements in R: The adehabitatLT Package.” Saint Benoist, Auffargis, France: Office Nationale de La Chasse. http://cran.gis-lab.info/web/packages/adehabitatLT/vignettes/adehabitatLT.pdf.

Dalla Rosa, L., E. R. Secchi, Y. G. Maia, A. N. Zerbini, and M. P. Heide-Jørgensen. 2008. “Movements of Satellite-Monitored Humpback Whales on Their Feeding Ground along the Antarctic Peninsula.” Polar Biology 31 (7): 771–81. doi:10.1007/s00300-008-0415-2.

Fauchald, P. & T. Tveraa. 2003. “Using First-Passage Time in the Analysis of Area-Restricted Search and Habitat Selection.” Ecology 84 (2): 282–88.

Friedlaender, A.S., E.L. Hazen, D.P. Nowacek, P.N. Halpin, C. Ware, M.T. Weinrich, T. Hurst, and D. Wiley. 2009. “Diel Changes in Humpback Whale Megaptera Novaeangliae Feeding Behavior in Response to Sand Lance Ammodytes Spp. Behavior and Distribution.” Marine Ecology Progress Series 395 (December): 91–100. doi:10.3354/meps08003.

Hazen, E.L., A.S. Friedlaender, M.A. Thompson, C.R. Ware, M.T. Weinrich, P.N. Halpin, and D.N. Wiley. 2009. “Fine-Scale Prey Aggregations and Foraging Ecology of Humpback Whales Megaptera Novaeangliae.” Marine Ecology Progress Series 395 (December): 75–89. doi:10.3354/meps08108.

Heide-Jorgensen, M. P., and K. L. Laidre. 2007. “Autumn Space-Use Patterns of Humpback Whales (Megaptera Novaeangliae) in West Greenland.” Journal of Cetacean Research and Management 9 (2): 121.

Kennedy, A.S., A.N. Zerbini, O.V. Vásquez, N. Gandilhon, P.J. Clapham, and O. Adam. 2013. “Local and Migratory Movements of Humpback Whales (Megaptera Novaeangliae) Satellite-Tracked in the North Atlantic Ocean.” Canadian Journal of Zoology 92 (1): 9–18. doi:10.1139/cjz-2013-0161.

Levin, S.A. 1992. “The Problem of Pattern and Scale in Ecology: The Robert H. MacArthur Award Lecture.” Ecology 73 (6): 1943. doi:10.2307/1941447.

Pinaud, D.D. & H. Weimerskirch. 2005. “Scale-Dependent Habitat Use in a Long-Ranging Central Place Predator.” Journal of Animal Ecology 74 (5): 852–63. doi:10.1111/j.1365-2656.2005.00984.x.