The total annual reproduction by a wildlife population is generally determined by 7 items. Each item may be influenced by habitat conditions and environmental factors (e.g., nutrition, weather, stress, disease, etc.). Because of this, a wildfire manager may have to measure several aspects of reproduction to understand an animal’s reproductive successes or failures.
So what are the 7 items that influence reproduction in wild animals?
1. Time of Onset of Breeding and Length of Breeding Season
- Influences the probability young will survive
- Influences numbers of litters/clutches produced
- Influences potential for juvenile breeding
The onset of breeding activities is controlled by photoperiod. Research has indicated local populations carry genes which help determine a response to the photoperiod that optimizes reproductive success under local conditions. These genes may be maladaptive in other areas – should be considered when talking about transplants or stocking.
The onset of breeding is often coordinated so that animals breed synchronously.
Advantages of Synchronous Breeding:
- Bring enough animals into breeding condition at one time to enhance fertilizaiton
- Coordinate reproduction with season of the year that optimizes birth and survival of young
- In some species, it fills the environment with newborns – so many young that predators may take a few during the short time the newborns are helpless
Disadvantages of Synchronous Breeding:
- A year of bad weather!
2. Number of litters (or clutches) produced per year
3. Litter or clutch size:
- Females experiencing their first pregnancy often have fewer ovulations and smaller litters than older females. Thus the age structure of a population may influence the total reproduction.
- *Nutrition is the factor most often implicated as influencing ovulation rates and litter sizes!*
4. Prenatal Survival: In mammals, prenatal mortality of embryos may account for differences observed between ovulation rates and the number of young born, e.g., brucellosis and Jackson Hole elk (cow elk have about a 90% pregnancy rate, but many of the embryos are aborted because of the presence of the disease brucellosis).
5. Viability of new born young:
- In mammals, nutrition is again the environmental factor most often implicated as influencing the viability of newborns.
6. Parental Care:
- Poor parental care is typical of first-time mothers
- Poor parental nutrition may result in reduction or failure of lactation (milk production)
- The amount of parental care needed will depend on the independence of the young at birth
Altricial: Helpless at birth (e.g., cottontails)
Precocial: Independent within hours after birth (e.g., hares)
Nidifugous: Leaves nest shortly after hatching (most waterfowl)
Nidicolous: Reared in nest (most songbirds, raptors)
7. Age of sexual maturity:
- And once more, nutrition affects at what age animals will breed! Poor nutrition can delay sexual maturity in mammals.
So what was the take home message for the best results for reproductive processes? If you provide for your wildlife’s nutritional needs, your animals can reproduce faster, and have more and more viable young! Whats to lose!