Directory UMM :Data Elmu:jurnal:S:Small Ruminant Research:Vol37.Issue1-2.Jul2000:

Small Ruminant Research 37 (2000) 73±84

Monitoring of estrous cycle of ewes by
ram-seeking behavior
R. Ortman*
Department of Biology, City College of New York, New York, NY 10031, USA
Accepted 6 December 1999

Abstract
For 6 years adult, non-synchronized Hampshire ewes (nˆ2, 5, 8, 8, 9 and 12) and rams (nˆ6, 10, 12, 11, 11 and 9) were
maintained separately and released to contiguous pastures having in common a woven-wire fence about 80 m long and 1.1 m
high. Natural estrous cycles were monitored daily by observations of ram-seeking behavior as de®ned as a ewe being
persistent in staying at the common fence with attention focused on the ram to the virtual exclusion of grazing. Day 0 of the
estrous cycle is the ®rst day that ram-seeking is observed. One hundred and thirty four fence stays and 115 estrous cycles have
been observed. For cycles falling within the normal range, the mean cycle duration (SE) was 16.530.03 days. During the
®rst four study years, a copulation test with an intact ram, carried out on a spot-check basis, indicated that all tested ewes
showing ram-seeking, except one, were in estrus. Ram-seeking never occurred outside of the estrous period of the cycle.
During the ®fth year, daily copulation tests with an intact ram and daily observations for ram-seeking has indicated that estrus
generally lasts about two days while ram-seeking lasts for one of these days, so that the two behaviors while overlapping are
not coextensive. During the sixth year, daily copulation tests with a vasectomized ram showed again a partial coincidence of
the two behaviors, but also that occasionally they appeared to have the same duration. It is concluded that the utilization of

ram-seeking provides an alternative, practical means to monitor the estrous cycle. # 2000 Elsevier Science B.V. All rights
reserved.
Keywords: Ram-seeking; Hampshire sheep; Estrous cycle; Copulation test; Cycle duration

1. Introduction
The search for the ram and movement toward him,
shown only by the ewe in estrus, has been referred to
as ram-seeking (Hart, 1985). This behavior was mentioned by McKenzie and Terrill (1937) and Grant
(1934) with free running animals, but demonstrated
*
Present address: 23, Barcomb-Ortman Way, Altona, NY 12910,
USA.

in paddocks utilizing tethered rams by Inkster (1957),
Lindsay (1966), Lindsay and Fletcher (1972) and
Allison and Davis (1976). However, the use of ramseeking as a primary means of monitoring the estrous
cycle apparently has never been reported (Bathaei,
1996).
The present paper describes the physical set-up in
which ram-seeking occurred and presents the data

obtained with its use to monitor the estrous cycle.
The mean duration of the normal cycle found in the

0921-4488/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 1 - 4 4 8 8 ( 9 9 ) 0 0 1 4 9 - 2

74

R. Ortman / Small Ruminant Research 37 (2000) 73±84

present study is remarkably similar to published
means for the same breed (McKenzie and Terrill,
1937) or other breeds (Bathaei, 1996).
During the ®rst 4 years of this study, ewes that
exhibited ram-seeking were checked sporadically for
estrus using an intact ram. In the ®nal 2 years of this
study, all ewes were observed daily for ram-seeking
and checked daily for estrus with an intact ram (1997)
or a vasectomized ram (1998). It has been found that
the abilities to show ram-seeking and estrus overlap

temporally, but are not necessarily coextensive. Preliminary ®ndings were reported earlier (Ortman,
1995).

2. Materials and methods
2.1. Animals and pastures
Adult Hampshire sheep were maintained in unisexual groups consisting of 2±12 ewes and 6±12 rams
depending on the year in question (Tables 1, 2 and 3)
in separate barns and released daily except on stormy
days and emergencies (footnotes, Table 1) to contiguous pastures. Rams were let out ®rst. A woven-wire
fence approximately 80 m in length and 1.14 m in
height separated these pastures. Visibility was unobstructed along this fence. Sheep had access to their
barns during the day and were con®ned to the barn
after dark at which time they were given hay and sheep
pellets (Agway). Water and mineral mix were supplied
ad libitum.
Each ewe was marked with a highly visible colored
spot (6±9 cm diameter) with stock marker (Donaghys)
placed in a unique location so that a ewe could be
identi®ed at a distance and in dim light (using binoculars, if necessary).
2.2. Ram-seeking behavior

Since the onset of ram-seeking behavior, as well as
its ®nal display, can take place at any time, observations on ram-seeking were carried out intermittently
throughout each day. A ewe that separates herself from
other ewes by coming to, and staying at, the common
fence with her attention focused on the rams on the
opposite side, to the virtual exclusion of grazing while
at the fence, was considered showing ram-seeking

(Figs. 1 and 2) (Hecker, 1983). The stay at the fence
can be relatively continuous or discontinuous with
brief intervals of absence from the fence for grazing.
The span of time from the ®rst observation of ramseeking until its terminal display or until the enclosure
of the ewe, whichever came ®rst, has varied from
about 0.5±11.5 h. Ewes showing ram-seeking for 1 h
or more have been scored R (Table 1) or ‡(Tables 2
and 3). Those few ewes exhibiting ram-seeking for
about 0.5 h have been scored (RB [Table 1] or ‡B
[Tables 2 and 3]). Ewes who made a momentary stop
at the fence while enroute to a grazing location were
not included. Finally, ewes considered as showing

ram-seeking must be close to the fence, so that the
distance of separation between the ewe's side and the
fencing was less than her width (Fig. 2), or that her
rostral end made contact with the fencing at some
point during her stay.
The ®rst day that ram-seeking was exhibited was
considered as Day 0 of the estrous cycle; the cycle
length is from Day 0 until the next day 0 (Hecker,
1983).
2.3. Copulatory test
To con®rm estrus in displaying ewes on a spotcheck basis during the ®rst 4 years of this study
(Table 1) they were captured at the fence, placed in
a mating room, and introduced to an intact ram. If the
ram mounted and began shallow thrusting movements
(Bermant et al., 1969), a ewe was considered to be in
estrus. If the ram failed to initiate sexual activity (a
rare event), he was replaced. In general, the copulating
pair was left together overnight. If the ewe was not in
estrus, the animals were promptly returned to their
respective groups. During the ®fth year (Table 2),

copulatory tests with an intact ram were given daily
to all ewes after they were secluded for the night. If a
ewe was in estrus, several copulatory sequences were
permitted. During the ®nal year, copulatory tests were
carried out with a vasectomized ram after enclosure
(Table 3).

3. Results
On being released from the barn, rams invariably
traveled to the common fence, apparently in anticipa-

Table 1
Dates of ram-seeking (R), test of sexual receptivity (C) to intact ram and parturition (Pa) in Hampshire sheepa
No. 34 b:
2/2/86

No. 33 b:
27/1/86

No.65 b:

18/3/93

No. 62 b:
2/5/92

No. 47 b:
10/4/90

No. 72 b:
19/2/95

No. 71 b:
30/4/94

No. 69 b:
24/4/94

No. 73 b:
3/3/95

1992
2 E (b)
6 R (b)

12/l0 R
28/11 RC
22/4/93 Pa

3/9 R
20/9 R
7/10 R
25/10 RC
18/3/93 Pa

±

±

±

±

±

±

±

1994
5E
l0 R

18/9 R
6/10 RC
3/3/95 Pa

25/9 RC
19/2/95 Pa

30/9 RC

27/10 RC

NR

±

±

±

±

1995 (c)
8E
12 R

1/10 RE
18/l0 R
5/11 R

21/11 RC
17/4/96 Pa

7/10 R
24/l0 RC
19/3/96 Pa

29/10 RE

7/11 R

20/11 RC
14/4/96 Pa

13/10
29/10
14/11
30/11

30/11 RO

NR

±

1996 (d)
8E
11 R

Ex (e)

21/9 R
8/10 R
25/10 R
11/11 RE
29/11 R(f)

31/10 R
16/11 R
2/12 RC

22/10 RE
10/12 RC

21/10 R
6/11 RC
3/4/97 Pa

13/11 R
30/11 RBC
23/4/97 Pa

5/11 R
20/11 RO
7/12 RO

30/10 RB
16/11 RC
14/4/97 Pa

18/10 R
7/12 RBC
7/5/97 Pa

R
R
R
R

R. Ortman / Small Ruminant Research 37 (2000) 73±84

Year (a) and
group size

a
Rˆewe displays ram-seeking (no test of sexual receptivity done); RBˆewe displays ram-seeking brie¯y; Cˆewe in standing heat to intact ram; Oˆ ewe not in standing heat;
NRˆno ram-seeking observed; ±ˆewe not born or not included; REˆram-see king extended into a second day; Paˆparturition; (a) no tests carried out in 1993; (b) Eˆewe, Rˆram;
(c) testing period 1/10±30/11; 29% of days no test; (d) testing period 21/9±21/12; 13% of days no test; (e) excluded (Ex) for reason of decrepitude; (f) not given test for sexual
receptivity because of her age.

75

76

Table 2
Daily testing of ewes for ram-seeking (R) and sexual receptivity (C) to intact rama

1997
9E
11 R

Ewe No.

62

65

69

71

72

73

74

75

81

Birth date

2/5/92

18/3/93

24/4/94

30/4/94

19/2/95

3/3/95

19/3/96

19/3/96

14/4/96

Test date
19/9
22/9
23/9
24/9
25/9±30/9a
1/10
2/10
3/10
4/10
5/10
6/10
7/10
8/10
9/10
10/10
11/10±20/10a
21/10
22/10
23/10
24/10
25/10
26/10±5/11
6/11
7/11
8/11
9/11
10/11

R
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡B
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡B
NT
ÿ
ÿ
ÿ
ÿ
‡B
ÿ
ÿ
ÿ

C
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
ÿ

R
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
ÿ
ÿ
ÿ
ÿ
ÿ
NT
‡
ÿ
ÿ
ÿ
ÿ
ÿ
‡
ÿ

C
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
ÿ
ÿ
‡
‡

R
ÿ
ÿ
ÿ
ÿ
ÿ
‡B
ÿ

C
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡
P

R
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡

C
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
P

R
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡B
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
NT

C
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡
P

R
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
ÿ

C
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡
P

R
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡

C
ÿ
ÿ
‡
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡
P

R
‡

C
‡
p

R
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

C
ÿ
ÿ
ÿ
‡
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
‡
P

R. Ortman / Small Ruminant Research 37 (2000) 73±84

Year and
group size

ÿ
‡
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡B
ÿ

ÿ
‡
‡
ÿ
ÿ
ÿ
ÿ
ÿ
‡
ÿ

ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
ÿ
ÿ
ÿ

12/12
Date of
parturition
(1998)

ÿ
±

ÿ

‡B
±

‡
25/2

3/3

16/3

5/3

3/3

13/2

5/3

a
Pˆpregnant; C‡ˆexhibits standing heat; Cÿˆdoes not exhibit standing heat; R‡ˆshows ram-seeking; Rÿˆdoes not show ram-seeking; R‡Bˆshows ram-seeking brie¯y;
NTˆno test; aˆdates inclusive.

R. Ortman / Small Ruminant Research 37 (2000) 73±84

11/11±21/11a
22/11
23/11
24/11
25/11
26/11±30/11a
4/12
7/12
8/12
10/12

77

78

Table 3
Daily observation of ewes for ram-seeking (R) with testing of ewes for sexual receptivity (C) to vasectomized ram during period 16/11 through 27/12
Year and
group size

1998
12 E
9R

47

62

65

71

72

73

74

75

81

84

87

88

Birth date
Test date

10/4/90

2/5/92

18/3/93

30/4/94

19/2/95

3/3/95

19/3/96

19/3/96

14/4/96

14/4/97

23/4/97

28/4/97

R

R

R

R

R

R

R

R

R

R

R

29/8
30/8
31/8±2/9a
3/9
4/9±10/9a
11/9
12/9
13/9
14/9
15/9±17/9a
18/9
19/9
20/9
21/9±27/9a
28/9
29/9
30/9
1/10±3/10a
4/10
5/10
6/10
7/10
8/10±10/10a
11/10
12/10
13/10
14/10
15/10
16/10
17/10
18/10
19/10
20/10
21/10
22/10

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
ÿ
ÿ
ÿ
‡
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
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ÿ

ÿ
ÿ
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ÿ
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‡
ÿ
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ÿ
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ÿ
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‡
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ÿ
ÿ

ÿ
ÿ

ÿ
ÿ
‡
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
‡
ÿ
ÿ
ÿ
ÿ
ÿ

C

C

C

C

C

C

C

C

C

C

C

R

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
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ÿ
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ÿ
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ÿ
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‡
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ÿ
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ÿ
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ÿ
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ÿ
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ÿ
ÿ
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ÿ
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‡B
ÿ

ÿ
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C

Note

R. Ortman / Small Ruminant Research 37 (2000) 73±84

Ewe

NT

NT

23/10±27/10a
28/10
29/10
30/10
31/10b

ÿ

ÿ

ÿ

ÿ

ÿ

ÿ

ÿ

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NT

‡
P

ÿ
ÿ
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NT

ÿ

‡
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ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
NT

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡

‡

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡
ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
‡

ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

‡

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ

ÿ
ÿ
ÿ
‡
ÿ
ÿ
ÿ

‡

ÿ
ÿ
ÿ
ÿ
‡
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

‡

‡
‡
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ
‡
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

‡

‡

ÿ
ÿ
ÿ
ÿ
‡
‡
ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
ÿ

ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ

ÿ

ÿ

ÿ

ÿ

ÿ

R. Ortman / Small Ruminant Research 37 (2000) 73±84

1/11
2/11
3/11
4/11
5/11
6/11
7/11
8/11
9/11
10/11
11/11
12/11±15/11a
16/11c
17/11
18/11
19/11
20/11
21/11
22/11
23/11
24/11
25/11
26/11
27/11
28/11
29/11±1/12a
2/12
3/12
4/12
5/12
6/12
7/12
8/12±9/12
10/12
11/12

ÿ

ÿ
NT
NT

79

80

Table 3 (Continued )

a

Ewe

47

62

65

71

72

73

74

75

81

84

87

88

Birth date
Test date

10/4/90

2/5/92

18/3/93

30/4/94

19/2/95

3/3/95

19/3/96

19/3/96

14/4/96

14/4/97

23/4/97

28/4/97

R

C

R

C

R

C

R

C

R

C

R

C

R

C

R

C

R

C

R

C

R

12/12
13/12±19/12a
20/12
21/12
22/12±23/12
24/12
25/12
26/12
27/12
28/12
Date of
parturition

ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
ÿ

ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
ÿ

ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
ÿ

ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
ÿ

ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
‡

ÿ
ÿ
ÿ
ÿ

‡
ÿ
ÿ

ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
ÿ

ÿ
ÿ
ÿ
ÿ

ÿ
ÿ
ÿ

ÿ
ÿ
‡
ÿ

ÿ
ÿ
ÿ

ÿ
ÿ
‡
ÿ

ÿ
ÿ
‡

C

R

C

‡
ÿ
ÿ
ÿ

ÿ
ÿ
ÿ

Note

NT
‡
‡
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
N/A

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
N/A

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
N/A

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
N/A

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
N/A

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
N/A

ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
ÿ
N/A

ÿ
ÿ
ÿ
ÿ
‡
‡
ÿ
ÿ
N/A

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
N/A

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
N/A

25/3/99

ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
N/A

Dates inclusive.
Intact ram used selectively on 4/10 and 31/10.
c
Vasectomized ram used exclusively 16/11 through 27/12; R‡ˆshows ram-seeking; R‡Bˆshows ram-seeking brie¯y; Rÿˆdoes not show ram-seeking; C‡ˆexhibits standing
heat; Cÿˆdoes not exhibit standing heat; Pˆpregnant; NTˆno tests on date.
b

R. Ortman / Small Ruminant Research 37 (2000) 73±84

Year and
group size

R. Ortman / Small Ruminant Research 37 (2000) 73±84

81

Fig. 1. Ewe No. 65 exhibiting ram-seeking by standing parallel to the fence. Two rams are on the opposite side.

Fig. 2. Ewe No. 65 showing ram-seeking by standing parallel to the fence with rams on the opposite side. Notice that her distance from the
fence is less than the width of her body. The ewe at far right is not showing ram-seeking.

82

R. Ortman / Small Ruminant Research 37 (2000) 73±84

tion of the arrival of the ewes. However, on most days,
the ewes, after leaving their barn, commenced to graze
and did not come to the common fence.
On an occasional day during the breeding season, a
single ewe (rarely two ewes) came to, and stayed at,
the common fence (Fig. 1). Such a ewe that has
separated herself from the ewe ¯ock was considered
as displaying ram-seeking behavior. Typically, the
ewe oriented herself parallel to the fence with her
head turned toward the rams but she continued to shift
her locus along the fence and to alternate the side of
her body next to the fence. Ewes have been observed
to stay at the fence from 0.5±11.5 h; during this time,
they did not graze. The dates on which ram-seeking
was shown and the results of the copulatory tests are
presented in Tables 1, 2 and 3 alongwith the birth dates of
the ewes and the group size for each year of the study.
Ram-seeking was closely linked to estrus. When
ewes showing ram-seeking were tested, on a spotcheck basis, for estrus, they always exhibited standing
heat except for No. 71, which was consistently not in
estrus (Table 1).
When ewes were tested daily for both ram-seeking
and estrus, it was found that ram-seeking was shown
only by ewes that were also in estrus (Table 2) except
for No. 71, which generally showed only ram-seeking.
No. 81 was unusual in that she did not show ramseeking, yet she exhibited estrus (Table 2). However,
in the next breeding season, she did show both behaviors once (Table 3).
In general, ram-seeking lasted only one day
whereas estrus lasted an additional consecutive day
(Tables 2 and 3). This difference in duration of the two
behaviors was found in six different ewes. In addition,
three ewes showed both behavioral reactions extending over 2 days. Two ewes showed the behaviors to
occur on adjacent days. Gaps in surveillance make it
impossible to know if the two behaviors are ever
con®ned to the same day.
The frequencies of estrous cycles of different
lengths are set out in Table 4. One hundred and four
cycles were obtained within the normal range (14±19
days). Their mean (SE) was 16.530.03 days. Four
possible double cycles and four possible triple cycles
as well as two short cycles and one cycle of 22 days
were also found.
After one copulation test with an intact ram, normal
pregnancies were obtained from ewes No. 33, 34, 47,

Table 4
Frequency of estrous cycles of speci®ed length in Hampshire ewes
determined by observations of ram-seeking
Cycle length (days)

No. of cycles

6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

1
0
0
0
1
0
0
0
0
12
40
38
13
1
0
0
1
0
0
0
0
0
0
0
0
0
0
3a
1a
0
0
0
0
0
0
0
0
0
0
0
0
1b
0
2b
1b
a
b

Possible double cycles.
Possible triple cycles.

69, 72, 73, 74, 75, 81 and 87. Ewes no. 62 and 65
remained barren in the 3 or 4 years, respectively that
they were given copulation tests. The successful

83

R. Ortman / Small Ruminant Research 37 (2000) 73±84
Table 5
Summary of results obtained with same-day testing for ram-seeking and estrus
Ewe shows ram-seeking

Ewe does not exhibit ram-seeking

Copulation test
positive

Copulation test
negative

Total
trials

Copulation test
positive

Copulation test
negative

Total
trials

No. of trials

49

5‡6ˆ11
(No.71)a

60

428

446

% Success in cop. test
% Success in cop. test
(excluding No. 71)

82
89

15b‡3ˆ18
(No. 81)
4

a
b

Consistently showed no estrus over 4 years.
[R‡ C‡] result occurred on previous or subsequent day.

pregnancy of ewe No. 71 in 1997 was quite unexpected.
The results of the investigation over 6 years are
summarized in Table 5. The overall success in the
copulation test was 82% with ewes showing ramseeking and 4% with those not showing ram-seeking.
If the atypical ewe (No. 71) is excluded from the
calculation, the percentages success in the copulation
test is 89%. The low percentage of success with ewes
not showing ram-seeking is probably accounted for by
continuance of estrus into Day 1 while, in general,
ram-seeking is not shown after Day 0.
The pregnancy of ewe No. 71 in 1997 was unanticipated since she never showed standing heat. It is
presumed that the ram managed to achieve intromission and ejaculation as he `rode' the ewe brie¯y while
she attempted to escape. However, she did show
standing heat to a vasectomized ram in the next year
(Table 3).

4. Discussion
Ram-seeking and estrus were studied separately in
alternate estrous cycles of synchronized ewes by
Lindsay and Fletcher (1972) and in different groups
of synchronized ewes by Allison and Davis (1976).
Both authors reported that the incidence of ram-seeking was signi®cantly less than the incidence of estrus.
However, at no time were the two behaviors studied in
the same animal on the same day. In the present
investigation, ram-seeking and estrus were found closely linked so that ram-seeking occurred during a part
of each estrous period. There are no observations that
ram-seeking occurred outside the estrous period of the

cycle or outside the breeding season itself. One ewe
(71) was considered abnormal since she was consistent in not showing estrus in testing over several years
despite exhibiting ram-seeking on a number of occasions.
Since the capacity to show ram-seeking lasts about
1 day while estrus generally lasts into the second day,
it is possible that ram-seeking is shown only while the
blood titer of estrogen is highest. Lindsay and Fletcher
(1972) believe that the estrogen requirement for ramseeking is greater than that for estrus.
Since ram-seeking is closely linked to estrus, it
should be possible to monitor the estrous cycle using
ram-seeking exclusively. Most of the cycles obtained
in this investigation (Table 4) were of normal length
(14±19 days.) having a mean duration (SE) of
16.530.03 days. The ewes measured were yearlings,
or older, and one lamb (in 1995). This mean compares
well to the means 16.01 (nˆ31) and 16.86 (nˆ289) for
Hampshire ewes (lambs included) tested with aproned
rams (McKenzie and Terrill, 1937) and to the means
16.0±16.7 for the second through ®fth cycles of
Hampshire lambs, tested with vasectomized rams
(Foote et al., 1970).
Since ram-seeking takes place on pasture, its observation is sensitive to disruption by very stormy
weather. Daily surveillance of ram-seeking during
the critical days when it might be shown (mean2
days) is required for a judgement on silent heats to be
made.
Table 4 shows four possible triple cycles and four
possible double cycles as well as short cycles. The
triple cycle shown by No. 73 (Table 1) may be due to
two silent heats in succession; the other three cycles
are problematic. Of the double cycles, those shown by

84

R. Ortman / Small Ruminant Research 37 (2000) 73±84

No. 62 and 88 (Table 3) may be due to one silent heat;
the other two cycles are problematic.
McKenzie and Terrill (1937) found that Hampshire
ewes showed short cycles as well as multiple cycles,
particularly double cycles. Multiple cycles were considered due to silent heats. Bathaei (1996) also attributed multiple cycles in Iranian Mehraban ewes to
silent heats. McKenzie and Terrill suggest that the
short cycles might be due to the early regression of the
corpus luteum. Ram-seeking is evidently a device that
will tend to increase the fecundity of the ewe.

5. Conclusion
Ram-seeking and estrous activity appear to be
concurrent, although not coextensive, behaviors of
non-synchronized Hampshire ewes showing natural
estrous cycles. It is concluded that the observation of
ram-seeking offers an alternative, practical method for
the monitoring of the estrous cycle.

Acknowledgements
The author wishes to thank Professor Norman
Schwartz of the Biology Department of City College
for photographic consultation and Patricia Macomber
for kind assistance with the photography.

References
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fertility of Merino ewes II. Effects of age of ewe, live weight,
and paddock size on duration of oestrus and ram-seeking
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Bathaei, S., 1996. Breeding season and oestrous activity of Iranian
fat-tailed Mehraban ewes and ewe lambs. Small Rumin. Res.
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Bermant, G., Clegg, M.T., Beamer, W., 1969. Copulatory behavior
of the ram, Ovis aries. I: A normative study. Anim. Behav. 17,
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Foote, W.C., Se®dbakht, N., Madsen, M.A., 1970. Puberal estrus
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Hecker, J.F., 1983. The Sheep as an Experimental Animal.
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Phenomena in the Ewe. University of Missouri, Agricultural
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