Biological Statistics of the Norway Rat


Basic rat statistics

Rats are extremely well studied animals, so we know an enormous amount about their basic biology. Here's a list of the Norway rat's basic biological data (Baker et al. 1979 and Weihle 1987, as reported in Pass and Freeth 1993; additional references noted below). For definitions of some of the terms and measurements used, see the next section.

Life span

 

Captivity

2-3.5 years

Pass and Freeth 1993

Wild

<1 year

Davis 1948

Weight

Birth

5-6 g

Pass and Freeth 1993

Weaning

30-55 g

Pass and Freeth 1993

Puberty

150-200 g

Pass and Freeth 1993

At 12 weeks: males

200-400 g

Pass and Freeth 1993

At 12 weeks: females

150-270 g

Pass and Freeth 1993

Adult: males

300-800 g

Pass and Freeth 1993

Adult: females

250-400 g

Pass and Freeth 1993

Developmental and life history events

Hair coat

9 days

Pass and Freeth 1993

Incisors erupt

8-10 days

Addison and Appleton 1915

Eyes open

12-14 days

Pass and Freeth 1993

Ear canal open

12-14 days

Pass and Freeth 1993

First leave nest to explore

14-16 days

Nelson 1995

First molars erupt

19 days

Addison and Appleton 1915

Second molars erupt

21 days

Addison and Appleton 1915

Weaning age

20-21 days (after 2nd molars erupt)

Pass and Freeth 1993

Faint yellow pigment appears on upper incisors

21 days

Addison and Appleton 1915

Faint yellow pigment appears on lower incisors

25 days

Addison and Appleton 1915

Descent of testes

15-50 days

Pass and Freeth 1993

Young rats first appear above ground

22-30 days

Adams and Boice 1983, Boice 1977

Third molars erupt

35 days

Addison and Appleton 1915

Puberty: males

39-47 days

Engelbrect J. T. et al. 2000, Chappel and Ramaley 1985, Korenbrot et al. 1977

Puberty: females

34-38 days

Engelbrect J. T. et al. 2000

Social maturity

160-180 days (5-6 months)

Adams and Boice 1983

Menopause (females)

450-540 days

Durbin 1966

Reproduction

Estrus cycle

4-6 days

Pass and Freeth 1993

Gestation

21-22 days

Pass and Freeth 1993

Litter size

6-14 offspring (varies with maternal age)

Pass and Freeth 1993, Mohan 1974

Maximum milk yield

12-14 days postpartum

Pass and Freeth 1993

Physiology

Rectal temperature

38-39º C

Pass and Freeth 1993

Heart rate

320-480 bpm (beats per min)

Pass and Freeth 1993

Blood pressure: diastolic

60-90 mm Hg

Pass and Freeth 1993

Blood pressure: systolic

75-120 mm Hg

Pass and Freeth 1993

Respiratory rate

85-110 breaths/min

Pass and Freeth 1993

Tidal volume

1.6 ml

Pass and Freeth 1993

Body surface area in cm2

9.1 x g0.66

Pass and Freeth 1993

Food consumption

Daily food consumption

5 g/100 g body weight

Pass and Freeth 1993

Daily water consumption

8-11 ml/100 g body weight

Pass and Freeth 1993

Urine

Urine output per day

5.5 ml/100g body weight

Pass and Freeth 1993

Urine osmolarity

1660 mOsm/kg of H20

Pass and Freeth 1993

Urine pH

7.5-8.5

Pass and Freeth 1993

Urine SG

1.04-1.07

Pass and Freeth 1993

Blood

Blood volume

5.6-7.1 ml/100 g body weight

Pass and Freeth 1993

Plasma volume

3.08-3.67 ml/100 g body weight

Pass and Freeth 1993

Red blood cell count

7-10 x 106cells/µl

Pass and Freeth 1993

Hemoglobin

11-19 gm/dl (dl = deciliter)

Pass and Freeth 1993

Packed cell volume

40.5-54%

Pass and Freeth 1993

Clotting time

2-5 min

Pass and Freeth 1993

Prothrombin time

8-4 sec

Pass and Freeth 1993

PTT

21.1 +- 3.7 sec

Pass and Freeth 1993

Fibrinogen

190 (150-230) mg/dl

Pass and Freeth 1993

Leukocyte count

Total

9(6-18) x 103/µl

Pass and Freeth 1993

Neutrophils

14-20%

Pass and Freeth 1993

Lymphocytes

69-86%

Pass and Freeth 1993

Monocytes

1-6%

Pass and Freeth 1993

Eosinophils

1-4%

Pass and Freeth 1993

Basophils

Rare

Pass and Freeth 1993

Platelets

500-1,000 x 103/µl

Pass and Freeth 1993

For those interested in a detailed summary of the timeline of neural development of the rat in utero, see Clancy et al. 2001.


Definitions


 


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