The California Wolf Center and HPWREN Collaborate on Real-Time Acoustics Sensors Project

Last year's installation of the HPWREN camera at the California Wolf Center, and the availability of its live feed, has enhanced the Center's ability to deliver educational programs both on-site and at remote locations, including classrooms, and has facilitated observation and management of the wolves by Center staff. A litter of pups was born at the Center in late April, and as they develop and spend more time out of the den exploring their environment, some of their interactions with each other and with the adult members of the pack that have been and will be recorded by the camera will provide interesting and useful information. The recent addition of an audio feed will allow pack vocalizations to be monitored, recorded, and used for educational and research purposes. Although the audio system is still being refined, some fascinating vocalizations had already been recorded.

Above: Seen on the left is the acoustics computer, with the microphone attached below the right side of the equipment box Right: Completed HPWREN access site with acoustics sensor at the California Wolf Center

Some immediate issues encountered were the impact of high wind situations at the Center, and a plan has been developed to research improvements by various wind shields, including foams, but also synthetic fur that was provided by the UCLA Center for Embedded Networked Sensing for this purpose.

Some initial wolf sounds were collected by streaming the audio across the network and collecting the data remotely, and processing it with the baudline spectrum analyzer. Results are seen in the sound samples and images below, with annotations by Kim Miller and Priscilla Hernandez of the California Wolf Center.

8.1MB sound file - (370kB MP3) The wolves of the California Wolf Center are often heard howling through the evening and even through the night. Howling is not only a way for wolf packs to establish territory boundaries with wandering lone wolves or neighboring wolf packs but it is also a way for the pack to reunite if members are spaced out within the territory or to strengthen bonds among individuals.

2.1MB sound file - (98kB MP3) From birth on, wolves are very vocal. This form of communication varies from moans, whines and squeals to growls, barks and howls. Each vocalization can convey aggression or friendliness depending on how large or small one sounds, regardless of the size of the animal. The larger you sound the more aggression you intend to convey. This pattern is seen amongst most mammals and birds (Mech, 2003). Here two female wolves, Naomi and Minka, convey aggression while one verbally asserts dominance over the other.

6.5MB sound file - (293kB MP3) A solo howl.

14.7MB sound file - (666kB MP3) Chorus howling is often highly contagious within a pack. This chorus is typically started by one wolf in the pack and the other members will join in at an accelerating rate.

0.8MB sound file - (37kB MP3) The signal is run through an about 200Hz high-pass filter to reduce the wind noise. Distant solo howl from one of the Mexican gray wolves. Mexican wolves, a smaller southwestern subspecies of gray wolves, once occurred in central Mexico and throughout portions of Arizona, New Mexico and Texas. As part of a captive breeding program for this rare and genetically distinct subspecies, the California Wolf Center is home to nine Mexican gray wolves. Over time staff members have come to identify the howl not only by it's location on site, but also by it's higher frequency.

After the wind issues are addressed, the intention is to collect the wolf sounds automatically as they appear, likely using the "listener" software, while making sound samples available in near-real-time in the California Wolf Center section of the HPWREN acoustics server.

By Dan Moriarty, PhD, Department of Psychology, University of San Diego, and California Wolf Center staff Kim Miller and Priscilla Hernandez