New research dives into the diversity of red foxes on Hokkaido Island, Japan, focusing on their physical characteristics, genetic traits, and unique population dynamics in specific areas.
Skull and Tooth Variations
Scientists studied 225 fox skulls and teeth (from 137 males and 88 females) to explore how their shapes and sizes vary across the island. They found small but meaningful differences among three genetically distinct groups identified in earlier studies. Key findings include:
Postorbital constriction (skull narrowing behind the eyes): This feature, linked to the size of chewing muscles, changes from west to east across the island.
Upper fourth premolar length (a large tooth): This varies between the southern and central groups and relates to overall body size.
Male foxes showed additional variations in skull width, height, and other features. Climate factors like temperature and snowfall likely influence these skull differences, alongside diet and food habits.
Genetic Diversity
The study examined the genes linked to immune system function in 232 foxes. Researchers discovered 17 new genetic variations and found that:
Southern Hokkaido foxes are genetically distinct from central and eastern foxes, likely due to geographic barriers like mountains and isolation.
Specific immune-related genes are evolving under “positive selection,” meaning they’re adapting to help foxes survive diseases and environmental challenges.
These genes show similarities with those of other fox species, suggesting long-term genetic sharing across species.
The Mt. Hakodate Fox Population
The isolated fox population on Mt. Hakodate (a small mountain near the sea) was studied using genetic data from fecal samples collected over three years (2009–2011). Key findings include:
The number of foxes fluctuated significantly: 20 in 2009, 5 in 2010, and 44 in 2011.
The fox density was surprisingly high compared to rural areas and even urban foxes in Zurich, Switzerland.
This population is strictly isolated due to natural barriers like the sea and surrounding rural areas.
Despite small territories, the foxes overlapped in their ranges, suggesting that abundant food (including human-provided food) helps sustain them.
Summary
The red fox population on Hokkaido shows fascinating diversity, shaped by climate, geography, diet, and human influence. These studies highlight how environmental and genetic factors interact to create unique populations on the island.
We would also note that;
"Umezawa Yusuke, a staff member of the Sapporo Northern Wildlife Park, pointed out that in the early Showa era (1926 ~ 1989 AD), people would import a kind of fox called "Silver Fox" to obtain their fur, and there were special processing factories at that time. . It is reported that the "Silver Fox" is a melanotic variant of the red fox. The coat colors include black all over (the end of the tail is white), blue-gray, and gray on both sides of the body."
These introductions and potential breeding with local foxes would also impact genetic structure and morphology.
Sources:
Morphological and population genetical studies on the red fox (Vulpes vulpes) of Hokkaido Island
A range-wide synthesis and timeline for phylogeographic events in the red fox (Vulpes vulpes)
Genetic Diversity of MHC Class II DRB1 Exon 2 in the Red Fox (Vulpes vulpes) on Hokkaido, Japan
Photo of Spirit, in memory of Jessie Hall
