Focus on Research
Penn State Intercom......January 30 , 2003


philtest copy

Groundhogs 'in love'

Male groundhogs hibernate less to visit the ladies

By A'ndrea Elyse Messer

Public Informationgroundhog

The days of gentlemen callers leaving their visiting cards are over, but if you are a male groundhog, visiting a few female burrows before the ladies come out in the spring may prove to smooth the way for later mating activities, according to a Penn State biologist.

"Field observations indicate that males immerge later and emerge earlier than females," said Stam M. Zervanos, associate professor of biology, Penn State Berks.

Zervanos defines the date of immergence as the last day they monitored the groundhog above ground in the autumn and he defines the date of emergence as the first date they monitored the groundhog above ground in the spring. Groundhogs do not simply crawl into their dens and hibernate, but rather they experience a series of torpor and arousal events throughout winter. During arousal events they stay in their burrows, but in the spring they emerge and move around above ground. They then return to the den for some more deep sleeping episodes before the final arousal for the season.

"Upon emergence, males tended to move within a given territory, often visiting female burrows," said Zervanos. "Females tended to stay close to their burrows." Zervanos observed one male at the entrance of a female's burrow about 300 yards from his home burrow. The female emerged and the male stayed with her for two days before moving on to another female's burrow. Afterwards, all three groundhogs stayed alone in their burrows experiencing episodes of deep torpor before final arousal.
"For males, these early excursions are an opportunity to survey their territories and to establish bonds with females," said Zervanos. "For females, it is an opportunity to bond with males and assess food availability."

Typically, groundhogs do not exit hibernation for good until early March, which is when they mate. These episodes of early visitation occur in February. It does not appear that mating occurs during these early encounters.

"The length of the hibernation season at a given location appears to be consistent for groundhogs -- also called woodchucks -- and is characterized by a predictable timing of immergence and emergence," Zervanos said. "This is important, because if mating occurs too early, young would be weaned at a time in the spring when food is still limited. If mating occurs too late, young would not have sufficient time to gain their critical hibernation weight."

Zervanos studied 32 free-ranging groundhogs over four hibernation seasons. Radio telemetry was used to monitor hourly body temperature from the groundhogs. A portion of the groundhogs at any one time were implanted with temperature transmitters. During the first two seasons, straw at the burrow entrances indicated if an animal had exited or entered a burrow, but for the final two years of the study, infrared motion triggered cameras were placed at the burrow entrances. These cameras recorded date and time of emergence as well as supplying a photograph.

On average, Zervanos found the groundhogs experienced first torpor on Nov. 7 and final arousal on Feb. 28. The average length of hibernation was about 114 days, but males exhibit significantly shorter hibernation seasons of about 106 days compared with females at about 117 days. The timing of hibernation activities did not vary significantly from year to year. Although males "tended" to immerge later and emerge earlier than females, no significant difference was observed.

"It would appear that the early bonding activity and establishment of territories in preparation for mating insure optimum conditions and timing for reproduction and offspring survival," Zervanos said.


A'ndrea Elyse Messer can be reached at aem1@psu.edu.

Class of composite organic material
could put muscle in artificial body parts

 

 

By A'ndrea Messer
Public Information RESEARCH_Zhang

A new class of all-organic composites that change shape under an electric voltage may openthe door for the manufacture of artificial muscles, smart skins, capacitors and tiny drug pumps, according to Penn State researchers.

"Electroactive polymers have been around for a long time, but the energy input required for them to do enough work to be of value was very high," said Qiming Zhang, professor of electrical engineering. "With this new composite we have reduced the voltage to one-tenth that previously needed."

The researchers report that a new class of composites, fabricated from an organic filler possessing very high dielectric constant dispersed in an electrostrictive polymer matrix, has much improved properties for the manufacture of actuators.

"These all-organic actuators could find applications as artificial muscles, smart skins for drag reduction, toys and in microfluidic systems for drug delivery," Zhang said. "In addition, the high dielectric constant makes this material attractive for high performance capacitors."

The dielectric constant is a relative measure of a material's ability to store electric charge. The dielectric constant is related to the chemical structure of the material and the higher the dielectric constant, the better the material will store an electric charge. Unlike traditional piezoelectric materials, which have a one-to-one relationship between voltage and movement, most electroactive polymers which are capable of creating large shape changes under electric fields have a square relationship between voltage and movement. In some cases, a 10 percent range of movement is attainable. The researchers looked at the electrostrictive poly(vinylidene fluoride-trifluoroethylene), a known electroactive copolymer which was developed recently at Zhang's laboratory, for the matrix in the composite. For filler, they used an organic semiconductor, copper-phthalocyanine, because it has a high dielectric constant.

"The copper-phthalocyanine disperses in the polymer matrix," Zhang said. "The dispersion is one aspect that we need to work on more and we are looking at a variety of approaches including creating nanocomposites." The composite has electrical properties more suitable to low voltage operation. The composites also are nearly as flexible as the copolymer alone which has the appearance of a slightly more rigid plastic bag.

"Potential applications for this material include a variety of tiny pumps because the material can be made to pump periodically or in a wave fashion, said Feng Xia, graduate student in electrical engineering and part of the team working on a variety of approaches to electrostrictive materials in the Materials Research Institute. "Small insulin or other pharmaceutical pumps could be powered by a low voltage battery and an electroactive composite. Other applications include pumping fluids through the channels in a diagnostic chip array or as smart skins that would reduce drag."

For artificial muscles and tendons, the flexible, elastic nature of the material may provide a more natural motion for mechanical musculature. Multiple, very thin layers stacked and then rolled and flattened could simulate muscles.

The team consists of Zhang; Xia; Hengfeng Li, post doctoral fellow in materials; Z.Y. Cheng, research associate; Haisheng Xu, post doctoral fellow; and Cheng Huang and Martin Poh, graduate student in materials research.

This work was supported by the National Institutes of Health, the Office of Naval Research and the Defense Advanced Research Project Agency. A patent has been filed on this research.


A'ndrea Elyse Messer can be reached at aem1@psu.edu.


Music selection may depend on
several factors, not just pleasure

Because people are fairly accurate in predicting which music will be most pleasurable to them, they should be given choices when music is being used to manage their moods and emotions, as in hospital rooms or during therapy, a Penn State study reports.

"Data from our analysis suggest that, while anticipated pleasure is a key reason for choice of music, Americans will also pick music to enhance mood or will match their musical selection with a specific activity such as jogging, aerobic dancing or reading a favorite book," said Valerie N. Stratton, associate professor of psychology at Penn State Altoona. Study participants also listed time of day and other people present as determinants in choosing a particular kind of music, she added. People also are capable of changing their minds about a song they initially dislike, noted co-author Annette H. Zalanowski, associate professor of music at Penn State Altoona. The researchers tested 20 study participants to see if, once they selected a musical piece based on pleasure, they still liked it after a specific period of listening. In most cases, they did. At the same time, however, participants listening to music they thought they wouldn't like, reported a higher degree of actual pleasure than what they anticipated.

For more of this story, go to http://www.psu.edu/ur/2002/musicexpectations.html.

 

PENN STATE'S RESEARCH HERITAGE

The Penn State Creamery in 1892 offered America's first collegiate instruction in ice cream manufacture, a program that has helped to make the University an international center for research in frozen confections.

Back