Ticks and Mosquitos: From mid-March to mid-July, grassy, brushy, low elevation areas (4000'-6500') are ideal tick habitat in Yellowstone. Wear repellent, tuck pant legs into boots, and tuck shirt into pants. Check clothes and body periodically.

During the summer season, mosquitoes are widespread, and especially concentrated in wet areas. Repellents, patience, forbearance, and wearing heavy clothing are the best options.

Pets: Pets must be leashed. They are prohibited on any trail, in the backcountry, and in thermal basins. Leaving a pet unattended and/or tied to an object is prohibited.

Firearms: No firearms, incuding state-permited concealed weapons, are allowed in Yellowstone. However, unloaded firearms may be transported in a vehicle when the weapon is cased, broken down or rendered inoperable, and kept out of sight. Ammunition must be placed in a separate compartment of the vehicle.

Falling Trees: Following the fires of 1988, thousands of dead trees, known as snags, were left standing in Yellowstone. Burned or unburned snags may fall with very little warning. Be cautious and alert for falling snags along trails, roadways, campsites and picnic areas. Avoid areas with large numbers of dead trees.

Sunburn: Untraviolet radiation is more intense at high elevations. It is much easier to get severely sunburned at high elevations than at sea level. Wear long sleeves and pants, a hat, and apply sunblock frequently. Protect eyes with sunglasses. Check infants and children as even slight redness can indicate potential sunburn.

Dehydration: The low humidity and high winds common at high elevations can quickly dry out the body. Dehydration can increase the risk of fatigue, hypothermia, and altitude sickness. Drinking plenty of water is the best protection against dehydration.

Altitude Sickness: At 9,000 feet, oxygen levels are about half that at sea level. Less available oxygen affects everyone differently, In some individuals, the effects are slight, perhaps unnoticeable, while in others, the changes bring on the more severe reactions of mountain sickness. Symptoms of altitude sickness may include:

• headache
• shortness of breath
• dizziness
• nausea
• fatigue
• nasal congestion
• rapid heartbeat
• diarrhea
• insomnia

If symptoms persist or worsen, go to a lower elevation as soon as possible and seek medical atention.

The best protection against altitude sickness is gradual acclimatization to higher elevations. Minimize risks by limiting strenuous activity the first few days. Rest, eat lightly, avoid alcohol, and increase intake of fluids.