Hungry Bears

Mark Ditmer holding a black bear cub

Mark Ditmer holding a black bear cub

If I asked you to name three favorite foods of bears, you would probably list off honey, berries, and salmon. But did you know that some bears also like corn and even sunflower seeds? Mark Ditmer, the Consbio program’s most recent grad, has spent the last several years studying what black bears eat in the far extreme of the Eastern black bear population’s range. His work attempts to explain how bears are managing to succeed in Northwestern Minnesota, an area previously thought to represent marginal habitat, but that is now the only part of Minnesota with an increasing bear population.

In order to survive a winter’s hibernation, bears need to pack on the pounds during the fall. Ditmer found that captive bears, given a choice, were basing their food intake on which items had the highest caloric content: fatty oil sunflower seeds were preferred over corn, acorns, and lower-calorie convection sunflower seeds. His stable isotope analysis of wild bears similarly showed that while corn and sunflowers made up a relatively small proportion of the available landscape, they were accounting for a disproportionately large amount of the diet.

As it turns out, crop fields provide easy foraging. By utilizing heart rate biologgers developed by Medtronic, Inc. and GPS-collars, Ditmer found that whereas when bears move across areas of open agricultural lands (without crops that bears prefer to eat) they exhibit faster movement and heart rates, their movement will actually decrease, and so may their heart rates, when they are foraging in crop fields. What could be easier than sitting in the middle of a corn field, and munching on every ear within arm’s reach? Of course, this kind of behavior gets bears into trouble with farmers. The havoc caused by a bear eating corn is much more visible than when a deer wanders through a field taking a bite here and a bite there.

So to answer Ditmer’s question, (how are bears managing to thrive in the marginal habitat of Northwestern Minnesota?) it turns out, bears in Northwestern Minnesota have much larger home ranges than bears in other places. Typically large home ranges are associated with poor habitats but Ditmer’s findings suggest that the males’ roaming is used to seek out and then hone in on the best available forage. Bear home ranges expand and contract in the short-term as different food resources become available. For instance, bears tend to stick to a smaller area if they have ripe crops in their home range, but before the crops ripen they are using a much larger area. As a general rule of thumb, the higher the caloric density (the more food there is) the smaller the bear’s home range will be. Crop fields are particularly dense in calories, so bears, especially the bolder males, are likely to use crops to forage to prepare for a long winter without any food. However, female bears seem willing to reduce or avoid raiding crop fields if other options in natural habitat, such as an oak forest full of acorns, are available in a given year.


CB PhD Student Jennifer Biederman featured on the Fisheries Blog

Current student Jennifer Biederman was featured as a guest contributor on the Fisheries Blog. Her post explores the relationship among reading, gender and science – and touches on what it’s like to be a new mom in graduate school. Enjoy!

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Cross-blogging on R

pair_plots CB doctoral candidate Marcus Beck has created an R-centric blog to highlight some tips and tricks he’s learned over the years. The focus is broad but he hopes to communicate some useful techniques using programmatic methods for data acquisition, organization, and analysis. He’s posted recent topics on data mining from the internet and modeling with different correlation structures. We encourage those of you that use R to head on over and have a look at some of his posts!

We are always in search of new blogs and strongly encourage graduate students to submit blog contributions. Topics can be wide-ranging, so long as they are relevant to Conservation Biology. Check out our submission page for the full range of topics and contact information for submission. Also, cross-posts are welcome if you manage an independent blog.

Here’s to a productive Spring semester!

Current Cons Bio grad student’s research featured in Nature film

Nature in HD, filmographers who specialize in capturing wildlife in the upper Midwest. spent some time with current graduate student Sarah Saunders and her research crew while conducting field work.

During the summers, the University of Minnesota banding crew travels throughout Michigan to band adults and chicks in the Great Lakes piping plover population in order to keep track of their numbers and identify individuals uniquely. Here, Nature in HD filmed a chick banding in Manistee on a hot July day. They began by using a spotting scope to look for the chicks on the beach, then slowly surrounded them and captured them with soft, harmless handheld nets. In total, the crew banded all 4 chicks and released them back to their parents.

Check out the video clicking this link.

Dispatch: Black Bear Research in Northern Minnesota

Check out this blog posting from Lisa O’Bryan (grad student in UMN’s EEB program and blogger for Women in the Wild) that chronicles an exciting weekend working with bears in Northern Minnesota, led by Conservation Biology PhD student Mark Ditmer.

Click to read: Into the Bear’s Den

CB Students Present and Receive Awards at The Waterbird Society’s 35th Annual Meeting

CB students Sarah Saunders and Gopi Sundar recently traveled to Annapolis, Maryland (along with other UMN students Linda Wires, Jennifer Stucker, and Kate Wyman) to present talks at the Waterbird Society’s 35th Annual Meeting. Both received awards. Here are the highlights:

From Sarah:

Annapolis (photo by Sarah Saunders)

In early November, I attended the The Waterbird Society 35th Annual Meeting in Annapolis, Maryland. It was a wonderful opportunity to meet and connect with waterbird and shorebird professionals and learn about the most recent research in the field. Symposia at the meeting featured talks on Oystercatchers, the impacts of the BP Deepwater Horizon oil spill on waterbirds, and conservation of Reddish Egrets, among others.

At the meeting, I learned a great deal about various waterbirds of which I was unfamiliar as well as new ornithological field methodologies. By speaking with some of the presenters one-on-one, I was able to learn more about their individual research topics as well as share information about my work. At the meeting, I gave an oral presentation entitled “Female Site Familiarity Increases Fledging Success in Piping Plovers.”  The abstract is provided below. This research was part of an analysis I started last fall with fellow co-authors: Erin Roche, Todd Arnold, and Francie Cuthbert. Acknowledgements for the presentation include: The Waterbird Society, University of Michigan Biological Station, UMN, and US Fish and Wildlife Service. The manuscript for this work is in review as a re-submission to The Auk.

Streets of Annaplis (photo by Sarah Saunders)

In addition to the meeting, I had time to explore the city of Annapolis. The historic downtown is home to the Naval Academy and maintains much of its history with brick streets, old-fashioned lampposts, and narrow streets.

Of course the seafood was delicious—especially the state specialty: crab. Conferences are a definitely a great chance to learn about developments in your field of interest, share and receive feedback on your research, and tour the sights of a new and exciting place!

Sarah received runner-up for Best Student Oral Presentation at the Waterbird Society annual meeting.


From Gopi:

I attended the 35th Annual Meeting of the Waterbird Society 9-12 Nov 2011, and featured over 120 talks of which more than one-third were student presentations. The meeting was attended largely by US-based researchers and students, but other countries represented included Canada, Iceland, and India. Two runner-up awards (one of which was awarded to Sarah!) and one Best Paper award was presented to student presenters. Other presenters from the Cuthbert lab at UMN were Linda Wires, Jennifer Stucker, and Kate Wyman.

My paper was titled: ” Simplified landscapes, complex patterns: Factors influencing waterbird abundance in the perennially cultivated Gangetic floodplains, India”. The abstract is included at the end of the blog posting. This research was part of my PhD work which I defended in CB in Sep 29th 2011. My committee members, in alphabetic order, were: Todd Arnold, Francie Cuthbert, Susan Galatowitsch, Nick Jordan, and Kristen Nelson. The work was supported by UMN, National Geographic Society, Waterbird Society, and the International Crane Foundation.

Gopi’s talk was adjudged the Best Student Paper in the conference.



Sarah Saunders – Runner-up for Best Student Oral Presentation @ Waterbird Society’s 35th Annual Meeting

Reproductive success commonly improves with age in birds. However, it is difficult to determine whether this phenomenon is due to breeding experience or other age-related factors as most potential explanatory factors are positively correlated. Using a 17-year database, we investigated how age, breeding experience, location experience, and pair-bond experience influenced Piping Plover (Charadrius melodus) reproductive success in the Great Lakes region. Reproductive success was measured as number of chicks fledged per pair for 415 successful nests during 1993-2009. We controlled for individual and site variation with random effects and tested for increased reproductive success associated with age and prior breeding experience, prior location experience, and prior pair-bond experience using generalized linear mixed models. Reproductive success increased with location-specific breeding experience of females and declined when females moved to a new location. After statistically controlling for these effects, we found no additional effect of male age, male experience, or pair experience. Additionally, fledging success declined with later hatching dates, so we examined the relative influence of age and experience on hatch date and determined that older females and males bred earlier. Our results indicate that improvement in reproductive success with age in Piping Plovers has two components: a direct effect of female location experience on fledging success, and an indirect effect of timing of breeding, which leads to greater reproductive success through earlier nesting by older males and females. Actions by resource managers to promote breeding philopatry and successful early nesting attempts may enhance reproductive success of this federally endangered population.


Gopi Sundar – Best Student Paper @ Waterbird Society’s 35th Annual Meeting

Waterbird abundance on agricultural landscapes is affected by multiple factors acting at different spatial scales, and seasonal effects due to changing crops. Using a multi-season landscape-scale design, I surveyed 24 districts in Uttar Pradesh state located in the crop-and-human dominated Gangetic floodplains to evaluate factors (extent of wetlands and landscape heterogeneity at two spatial scales; intensity of cultivation or IOC; location; and season) affecting waterbird abundance. Wetland birds dominated (37%) sampled bird species richness (229 species). Indicator species analyses identified 16 waterbirds affected by IOC, 75% of which were associated with the lowest IOC. The smallest number of indicator species occurred during the rainy season when rice-paddies were the primary crop suggesting high homogenization in that season. I used hierarchical partitioning to understand the relative importance of explanatory variables for waterbird abundance. Total waterbird abundance was influenced most by extent of remnant wetlands at the smaller spatial scale suggesting weak landscape-scale effects due to simplification. Species abundance was influenced by different variables (primarily wetland extent and landscape heterogeneity at different spatial scales;IOC; location), and patterns varied with season suggesting different individual responses corresponding to seasonal landscape conditions. To maximize waterbird abundance on Uttar Pradesh’s simplified landscape, relatively complex interventions at both spatial and temporal scales appear to be required. These include improving wetland habitat especially in areas with high intensities of cultivation, and understanding which locations experience proportionally higher wetland reduction in the dry season.

Have you recently traveled to a meeting? Give your fellow CB’s a report on how it went! Submit posts to Jennifer Biederman (