How gophers breathe underground has been the subject of debate and scientific studies for many years. The most comprehensive study to approach this subject is the article, “Respiratory adaptations in burrowing pocket gophers from sea level and high altitude.” The study was written by Andrew J. Lechner and was published in the Journal of Applied Physiology in 1976.
This article summarizes Lechner’s scientific study in more general terms that everyday readers can more readily understand.
The summary is, “Gophers are able to breathe underground through physical adaptions that include, lower need for oxygen, increased blood tolerance for elevated carbon dioxide levels and an increased ability to store and transport oxygen.”
Let’s look at each of these factors in more detail.
Burrow Air Quality
To fully appreciate a gopher’s ability to breathe in a burrow it is important to understand the composition of the underground air.
At sea level the atmospheric concentration of oxygen is 20.9% and carbon dioxide is about 0.04%.
Inside a gopher burrow the oxygen levels have been measured as low as 15% and the carbon dioxide levels as high as 5%. This means that gophers have to deal with both low oxygen and high carbon dioxide conditions.
The low oxygen situation is not that problematic as a 15% oxygen concentration is about the same as we experience at higher altitudes. In fact, a 15% oxygen concentration is just about what you will find everyday in Aspen, Colorado.
The real trick has to do with the elevated carbon dioxide concentration. A carbon dioxide level of 5% is toxic to humans and will lead to death if exposure continues.
Lower Metabolic Demand
Gophers generally have a Standard Metabolic Rate that is about 75% of what is predicted based upon their size. This means that, for some reason, gophers do not need as much oxygen as similarly sized animals to survive.
Additionally, gophers have the ability to lower their core body temperature by a few degrees. As their body temperature drops gophers need even less oxygen to survive.
Increased Myoglobin
In addition to have an inherently lower need for oxygen than similarly sized animals it appears that gophers are also better at storing and utilizing what oxygen is available.
When compared to similarly sized rodents such as rats, it was found that gophers have an increased amount of myoglobin. Myoglobin is the protein that helps transport oxygen through our bodies.
Gophers and rats have about the same amount of myoglobin in their cardiac muscles but gophers have an extra store of the protein in their skeletal muscles.
Buffering Capacity and Blood Tolerance to CO2
The low metabolic rate and increased myoglobin are two ways that gophers deal with low oxygen concentrations. But how do they handle toxic carbon dioxide levels?
The study by Lechner found that gophers have a unique blood system.
It is important for a living creature to maintain the right level of acidity in its blood and, for most animals including gophers, this value corresponds with a pH of about 7.4.
The blood acidity level is controlled by the amount of:
- Carbonate/Carbonic Acid
- Phosphates
- Hemoglobin
- Plasma Proteins
When gophers breathe air that has a high concentration of carbon dioxide the Carbonate/Carbonic Acid levels become unstable. Gophers compensate for this and maintain a consistent blood acidity by having increased levels of phosphates and hemoglobin.
Conclusion
Gophers are able to tolerate the low oxygen levels in underground burrows by using less oxygen and having more myoglobin to transport the available oxygen.
Gophers are able to survive the toxic carbon dioxide levels through a unique blood chemistry that maintains a stable pH through elevated phosphate and hemoglobin levels.
Pretty neat stuff!
