Animals and cold weather

While most of us can warm ourselves with a heater or blanket, animals do not have that luxury in winter.

Like humans, warm-blooded animals must maintain a certain internal body temperature. A cold spell can cause death and injury to livestock and wildlife. If an animal’s core body temperature drops below 35 degrees Celsius, they can die of hypothermia. Exposure of body extremities (ears, tail and distal limbs) to temperatures below zero can result in frostbite.

Most species have developed different behaviours and adaptations to manage the cold.

Some examples being: A few of the African antelope species can build up significant (protective) subcutaneous fat reserves. In addition, most are pregnant during our dry, cold winter months. This puts additional nutritional strain on the animals. Some species, such as kudu, nyala and warthogs are more sensitive to cold than others. We thus often see mortalities in these species - not so much warthog, because they shelter in relatively warm ground boroughs - whilst frost bite and the dropping off of ear tips in sable and roan is not uncommon.

Why are small animals more susceptible to cold stress?

Smaller animals have, on a per kilogram basis, a much higher energy consumption to fulfil their basic daily functions.

As soon as there is a dietary energy deficiency - typical Namibian winter and drought situation - the mere fight for survival places a severe strain on body reserves. This is exacerbated by advanced pregnancy and lactating in females.

A large surface area leads to a greater heat loss per unit mass of animal. To compensate for this higher heat loss, a mammal's metabolic rate has to be sufficiently high to maintain its body temperature at a steady value of say 38 degrees Celsius.

Thus, the bigger an animal, the lower its heat loss relative to its size, resulting in more modest food requirements (not in the absolute sense of the total amount of food ingested, but relative to their body size, i.e. kilogram of food per kilogram of body mass).

The end result is a “relatively low running cost” for these big animals. The average elephant weighs 220 000 times as much as the average mouse but requires only about 10 000 times as much energy to sustain itself.

The bigger the animal, the more efficiently it uses energy.

How different species adapt to handle the cold:

- Sleep and hibernate: Some species go into a deep sleep and slow down their heart and breathing rate – this is called hibernation. Some mouse and bird species only go into a ‘deep sleep’ phase for a few hours or days when it’s extremely cold. This is called torpor.

- Migration: Especially birds migrate to warmer areas before the cold winter months are coming.

- Minimising exposure to cold winds. In severe cold and windy spells, animals are classically observed sheltering in densely bushed areas which serve as wind shelters.

- Physiological changes such as growing thicker fur, building fat reserves, raising hairs on the body to trap heat, or fluff up feathers.

How to maintain good body condition:

- Good quality food: Providing this food (ideally hay/roughage) in the late afternoon will stimulate rumen microbes to digest hay to provide the ruminant with nutrients while fermentation in the rumen produces (at no energy expenditure for the animal) heat to protect your animals.

- Water and boma/kraal hygiene: Animals’ water consumption increases because of elevated metabolic rates necessary to maintain warmth. Make sure water is clean, free of ice, and in adequate supply. To minimise heat loss avoid keeping animals in wet, muddy kraals.

- Shelter and debushing: Trees, land windbreaks, other natural weather barriers and constructed shelters will assist in blocking winds.

- Additional shelter: These are very effective, but, especially for wild animals, must be constructed early in the winter, close to feeding and drinking sites, to allow the animals time to get used to the structure and enter it on cold nights. Such a ‘maze’ should obviously have multiple openings to allow easy entrance and exit.

- Concentrating animals: Try concentrating animals into sheltered spaces so that proximity to other animals provides some form of shelter and heat.

- Bedding: Keep bedding as dry and clean as possible to avoid increased ammonia fumes which can irritate the respiratory lining of livestock thereby increasing susceptibility to pneumonia.

- Monitor: During extreme cold spells animals should be monitored often. Specifically monitor the young/smaller animals (such as nyala) that are more at risk to cold temperatures. Care for young animals first, since they have lower body energy stores and are more vulnerable than larger animals.

- Buy animals from areas similar to yours: This gives some guarantee of the animals being more cold-adapted thus hopefully reducing your losses in a harsh winter.