Reproductive activity in captive female cheetahs (Acinonyx jubatus)

assessed by faecal steroids

J. L. Brown, D. E. Wildt, N. Wielebnowski, K. L. Goodrowe,
L. H. Graham, S. Wells and J. G. Howard
Conservation and Research Center, National Zoological Park, Smithsonian Institution, Front Royal,
VA 22630, USA; Department of Wildlife and Fisheries Biology, University of California, Davis,
CA 95616, USA; 3Metro Toronto Zoo, Scarborough, MlB 5K7, Ontario, Canada; and ^Department of
Mammals, National Zoological Park, Smithsonian Institution, Washington, DC 20008, USA

Faecal oestradiol and progestogen metabolite excretion was monitored in adult, female
cheetahs (Acinonyx jubatus) (n= 26) for 1\p=n-\24months. Increased faecal oestradiol excretion
was associated with mating or equine chorionic gonadotrophin (eCG) administration for
artificial insemination, whereas increased progestogen metabolites were observed during
natural and human chorionic gonadotrophin (hCG)-induced pregnant and nonpregnant
luteal phases. On the basis of oestradiol excretory patterns, duration of the oestrous
cycle (mean \m=+-\SEM) was 13.6 \m=+-\1.2 days with high oestradiol concentrations lasting for
4.1 \m=+-\0.8 days. In non-gonadotrophin-treated cheetahs, 75% showed evidence of oestrous
cyclicity; however, none evaluated for 1 year or longer were continuously cyclic. Rather,
cyclicity was interrupted by periods of anoestrus, often exceeding several months in
duration. These inactive ovarian periods were unrelated to season and were not synchro-
nous among females. Mean duration of gestation (breeding to parturition) was 94.2 \m=+-\0.5

days, whereas duration of faecal progestogen metabolite excretion during the nonpregnant
luteal phase was 51.2 \m=+-\3.5 days. On the basis of progestogen metabolite evaluations,
spontaneous ovulation (non-mating induced) occurred only once in two females (2 of 184
oestrous cycles; 1.1%). Peak eCG-stimulated, preovulatory oestradiol concentrations were
similar to those associated with natural oestrus, whereas progestogen metabolite profiles
after hCG resembled those during pregnant and nonpregnant luteal phases after natural
mating. In summary, results confirm that the cheetah is polyoestrus and ovulation is
almost always induced. However, new evidence suggests that many females inexplicably
experience periods of anoestrus unrelated to season, while 25% of the cheetahs examined
expressed no ovarian activity during the study period.

Introduction of zoo-maintained cheetahs have

ever reproduced and infant

mortality, usually related maternal neglect, averages

to
It is estimated that fewer than 15 000 wild cheetahs (Acinonyx 30-40% (Marker and O'Brien, 1989; Marker-Kraus and
jubatus)remain in southern and eastern Africa, and their Grisham, 1993).
continued existence is threatened by many factors, including Possible of poor fertility in captivity were determined
causes

prédation and competition by other carnivores, especially lions by conducting areproductive survey of North American
and hyenas, and extermination by humans (Laurenson et al, cheetahs (sanctioned by the Cheetah Species Survival Plan)
1992; Marker-Kraus and Grisham, 1993; Caro, 1994). Cheetahs between January 1990 and June 1991 (Wildt et al, 1993). In
in captivity and in the wild also suffer from a lack of genetic general, reproductive tract anatomy and pituitary function
diversity which may negatively impact reproductive function were normal in most adult females irrespective of breeding
and affect long-term survival (O'Brien et al, 1983, 1985). Even success. Furthermore, although male cheetahs naturally produce

so, the reproductive rate of free-ranging cheetahs appears to be a high proportion of malformed spermatozoa (Wildt et al,

relatively high with perhaps 80% of adults producing offspring 1983, 1987), there were no differences in seminal quality
during their lifetime (Laurenson et al, 1992). In contrast, the between proven and unproven breeders (Wildt et al, 1993). In
species has proven difficult to breed in captivity despite contrast, > 50% of females appeared acyclic on the basis
considerable effort (Guggisburg, 1975). Only about one-third of laparoscopie observations of inactive ovaries combined
with parallel, one-time measurements of baseline circulating
Received 1 September 1995. ovarian steroids. This survey was the first organized and
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comprehensive attempt (60 males:68 females at 18 institutions) Toronto Zoo were fed ground horsemeat supplemented with
to identify possible biological causes of poor reproduction in minerals/vitamins and whole carcasses (rabbit, guinea pig).
cheetahs and suggested that poor fecundity in captivity may
reflect suboptimal husbandry and management conditions
rather than a fundamental loss in reproductive fitness. Longi¬ Semen collection, induction of ovulation and artificial insemination
tudinal studies now are needed to evaluate more fully the
dynamics of reproductive steroid secretion in this species. Electroejaculates for artificial insemination were collected
from two males at the Caldwell Zoo (6 and 7 years of age).
In the
present study, non-invasive faecal steroid monitoring Semen was collected under ketamine HC1 (15-20 mg kg-1,
was used to evaluate reproductive events in cheetahs to
confirm and explain the apparent lack of ovarian cyclicity. In i.m.; Vetalar"; Parke-Davis, Morris Plains, NJ) anaesthesia
administered via a projectile dart as described by Howard et al
addition, new data were generated on the 'normality' of
ovarian responses to exogenous hormonal ovulation induction
(1992). In brief, an AC sine-wave electroejaculator with rectal
and artificial insemination protocols by comparing faecal probe was used in a regimented sequence consisting of 80
steroid profiles in pregnant versus nonpregnant animals after incremental electrical stimuli (3-7 volts) given in an on—off
natural mating. pattern in three series over about 20 min (Wildt et al, 1983,
1987, 1993). Total ejaculate volume, sperm cell concentration
and progressive motility of spermatozoa were determined as
described by Wildt et al (1983, 1987, 1993), and Howard et al
Materials and Methods (1992). Each ejaculate was diluted (1:1) with Ham's FIO
medium (Irvine Scientific, Santa Ana, CA) containing 5% (v/v)
Animals and faecal sample collection heat-inactivated fetal calf serum (Irvine Scientific), centrifuged
(at 300 g for 10 min); the supernatant was discarded and the
Study animals included adult, female cheetahs maintained at:
the Phoenix Zoo, Phoenix, AZ (n 4; 5.8 ± 3.4 years of age,
= sperm pellet resuspended gently in 250—300 µ of fresh Ham's
FIO medium (Howard et al, 1992).
range 3—10 years); the Metro Toronto Zoo, Toronto (n 3;
= =

Cheetahs designated for artificial insemination were induced

5.7+ 1.7 years of age, range 3.5-9 years); the White Oak
=

to ovulate using a gonadotrophin regimen established by

Conservation Center, Yulee, FL (n 8; 6.4 + 1.2 years of age,
=

Howard et al (1992). In brief, equine chorionic gonadotrophin

range 2.5-12 years); the Sacramento Zoo, Sacramento, CA
=

(n 2; both 2.5 years of age); and Wildlife Safari, Winston,

=
(eCG; 200 iu; Sigma Chemical Co., St Louis, MO) and human
OR (n 6; 5.5 ± 1.7 years of age, range = 3-13 years). Five
=
chorionic gonadotrophin (hCG; 100 iu; Sigma Chemical Co.)
were injected i.m., 80 h apart to stimulate follicular develop¬
animals at the White Oak Conservation Center and the two
ment and ovulation, respectively. Intrauterine insemination was
Sacramento Zoo cheetahs were monitored on two separate
occasions. Three additional females maintained at the Caldwell performed laparoscopically about 45 h after hCG injection
Zoo, Tyler, TX (8.3 + 2.2 years of age, range 4-11 years)
= using a method similar to that described by Howard et al
were subjected to ovulation induction for laparoscopie artificial
(1992). Anaesthesia was induced with ketamine HC1 (5—10 mg
insemination (see below) twice, at an interval of eight months. kg 1, i.m.) and xylazine (0.5-2 mg kg \ i.m; Rompun®',
- ~

Faecal samples were collected 3—7 times a week from all Miles Laboratory, Inc., Shawnee Mission, KS) administered via
a projectile dart. Surgical anaesthesia was maintained with
cheetahs for periods of 1—24 months and were stored frozen
isoflurane gas-oxygen administered via intubation. Each chee¬
( 20°C) in 50 ml conical polypropylene vials until processed. tah was placed in a supine head-down position, a pneumo-
Cheetah management differed markedly among institutions
-

making it impossible to correlate husbandry practices with peritoneum produced and a 10 mm laparoscope (Olympus
specific biological events. Social groups and caging situations Corporation, Lake Success, NJ) inserted at the midline. An
also varied throughout the year even within institutions. accessory grasping forcep was used to stabilize the uterine
horn and an 18-gauge catheter (Sovereign", Sherwood
However, there was consistency in that all animals were
Medical, St Louis, MO) was inserted transabdominally into
exposed to natural fluctuations in photoperiod and each each uterine horn as a conduit for sterile polyethylene tubing
institution had a least one male housed within olfactory
(PE-10; Intramedic", Clay Adams Parsippany, NJ) containing
proximity to females. In general, females were housed with about 10 x 106 motile spermatozoa in Ham's FIO medium. The
other females (at least occasionally) and, with the exception of
PE tubing was placed into the uterine lumen beyond the tip of
one cheetah at the Wildlife Safari and two at the White Oak
the catheter and the diluted spermatozoa (125-150 µ per horn)
Conservation Center, all had been exposed to males for
breeding (although not necessarily during the study period).
were expelled.
Breeding strategies varied: some females were introduced to a
male on a single day when she appeared in oestrus (affective
Faecal steroid analysis
behaviour, rolling, calling or lordodic posturing), whereas
others were housed with a male for various time periods (days Faecal oestradiol and progestogen metabolites were
or weeks). Cheetahs at the Sacramento Zoo, Phoenix Zoo and extracted from samples as described by Brown el al (1994,
White Oak Conservation Center were fed Nebraska Canine 1995). Briefly, samples were lyophilized, pulverized and
Diet (North Piatte, NE), supplemented weekly with bones, about 0.2 g well-mixed powder boiled in 5 ml aqueous ethanol
chicken carcasses or horse ribs. Cheetahs at the Wildlife Safari 90% (v/v) for 20 min. After centrifuging at 500 g for 10 min,
were fed carcass meat only (horse, cow, deer, chicken, turkey)
supernatant was recovered and the pellet resuspended in 5 ml
supplemented with calcium and vitamins. Animals at the Metro 90% ethanol, vortexed for 1 min and re-centrifuged. Both
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 ethanol supernatants were combined, dried completely and values and remained high for at least 1 week. Mean pro¬
then redissolved in 1 ml methanol. Extractants were vortexed gestogen metabolite concentrations during pregnant and non¬
(1 min), placed in an ultrasonic cleaner for 30 s and re-vortexed pregnant luteal phases contained values from the time of
(15 s). Samples were diluted (1:40 for oestradiol; 1:800- observed mating or artificial insemination to parturition or the
1:80 000 for progestogens) in PBS (0.01 mol P04 1 \ 0.14 mol
"
sustained return of progestogen metabolite excretion to base¬
NaCl 1, 0.5% (w/v) BSA, 0.01% (w/v) NaN3) before line values. Weekly or three times weekly means were calcu¬
analysis. Recovery of [ H]oestradiol and [I4C]progesterone lated for each individual female and then averaged to provide
(New England Nuclear, Wilmington, DE) added to faecal the respective group means. Differences in preovulatory peak
samples before extraction exceeded 90%. oestradiol concentrations or mean progestogen metabolite
Faecal oestradiol and progestogen metabolites were concentrations between pregnant and nonpregnant luteal
quantified using radioimmunoassays validated for cheetahs as phases, or gonadotrophin-treated versus naturally mated
described by Brown et al (1994). The oestradiol radio¬ females, were determined using Student's I tests. Data are
immunoassay relied upon an antibody provided by S. Wasser presented as means ± sem.
(Center for Wildlife Conservation, Seattle, WA) (Risler et al,
1987), a 3H-labelled oestradiol tracer (New England Nuclear)
and oestradiol standards. This assay specifically quantified Results
faecal oestradiol, with minimal crossreactivity ( < 2%) with
other faecal oestrogen metabolites (oestradiol sulfate and
General observations
oestrone). The progesterone radioimmunoassay relied upon
a monoclonal progesterone antibody produced against On the basis of 184 cycles from 18 individuals, oestrous
4-pregnen-ll-oI-3,20-dione hemisuccinate:BSA (331; provided cycle duration was 13.6 ± 1.2 days (range, 5—30 days) with
by J. Roser, University of California, Davis, CA), an increases in oestradiol concentrations lasting 4.1 ± 0.8 days
I25I-Iabelled progesterone tracer (ICN Biomedicai, Inc., Costa (range, 1-14 days; = 132 cycles). When partitioned by
Mesa, CA) and progesterone standards. The assay specifically duration, the percentages of oestrous cycles < 7, 8-13, 14—19
quantified the major conjugated progestogen metabolite(s) and and >20 days in length were 20, 28, 35 and 17%, respectively.
several free pregnanolone epimers (Brown et al, 1994). Assay There was considerable variation in the duration of the
sensitivities, based on 90% of maximum binding, were 5 pg per oestrous cycle, both within and among individuals. For females
tube and 7.5 pg per tube for the oestradiol and progesterone evaluated for > 1 year, overall mean duration of the oestrous
assays, respectively. Intra- and interassay coefficients of varia¬ cycle (average of all oestrous cycles for each individual) ranged
tion were < 10% for both assays. All faecal data are expressed from 10.4 ± 1.0 to 19.0 ± 2.2 days. Even within a female,
as g ~ dry mass. oestrous cycle duration typically spanned the entire range from
< 7 to > 20 days.
Baseline oestradiol concentrations generally ranged from
~l
Statistical analyses 25—60 ng g dry faecal mass with peak concentrations
ranging from 100 to 750 ng g There were no differences
Significant increases in faecal oestradiol concentrations were (P > 0.05) in peak preovulatory oestradiol concentrations
.

determined by an iterative process in which high values were between animals that conceived (284.3 ± 45.5 ng g ;
~

excluded if they exceeded the mean + 1.5 sd. Baseline values =

5) and those that mated but did not conceive
were those remaining after all high values had been excluded. (314.8 ± 41.9 ng g~ 1; n = 8) (Fig. 1). Similarly, there were
The duration of the oestrous cycle was calculated as the no differences (P > 0.05) in preovulatory oestradiol concen¬
number of days between peaks in oestradiol concentrations trations between naturally-mated and eCG-treated (281.0 +
(presumed tobe associated with oestrus) for periods not 39.6 ng g ; n = 6) females (Fig. 1). Peak oestradiol concen¬
~

exceeding 30days (that is, > twice the estimated oestrous trations in nonmated females averaged 302.1 ± 12.3 ng g~ .

cycle duration: Eaton and Craig, 1973; Bertschinger et al, 1984; Faecal oestradiol excretion during pregnancy tended to remain
Asa et al, 1992). Interoestradiol peak intervals > 30 days were at baseline values until several weeks before parturition,
considered as anoestrous periods. The number of days on when concentrations increased up to tenfold and then
which oestradiol was raised above baseline (indicative of declined after parturition (Fig. 1). In contrast, mean oestradiol
oestrus) was calculated only during periods when faecal concentrations during the nonpregnant luteal phase
samples were collected for a minimum of five times per week. generally remained at baseline values, although random peaks
Data from females monitored < 60 days and during pregnant occasionally occurred.
and nonpregnant luteal phases were not included in oestrous Average baseline faecal progestogen metabolite concen¬
cycle calculations. In females subjected to induction of ovula¬ trations among individuals ranged from 0.7 to 6.0µgg~
tion and artificial insemination, baseline oestradiol concen¬ Faecal progestogens in ovulating females increased within .

trations were calculated from all samples before induction of 1—10 days of the oestradiol surge. In pregnant females,
ovulation. The beginning of the oestradiol surge was deter¬ concentrations remained 100- to 400-fold greater than baseline
mined by a value that exceeded preceding values by 50%. Basal throughout gestation, rarely decreasing to less than 20-fold
progestogen metabolite concentrations were calculated from over baseline until near parturition (Fig. 1). There were no
values preceding preovulatory oestradiol surges. Postovulatory differences (P>0.05) in overall mean progestogen metabolite
increases in progestogen metabolite excretion were considered concentrations between pregnant (202.9 + 15.3 µg g1) and
significant if values exceeded the mean ± 2 sd of the preceding nonpregnant (240.6 ± 26.4 µg g ) cheetahs during the period
~

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 600 - (a) r- 400

Mating 300
400

200

200 -

100

600 (b) 400

Mating
300
400

g 200

<8 200
o
-
100 Q-

600 -i (C) r- 400

300
400 -

200

200

100

40 60 80 100
Days from oestradiol peak
Fig. 1. Mean (± sem) faecal oestradiol ( ) and progestogen (·) metabolite concentrations in (a) pregnant (n 5) and (b)
=

nonpregnant (n 8) cheetahs after natural mating and in (c) nonpregnant cheetahs after induction of ovulation by
=

gonadotrophin and artificial insemination ( ) ( 6). Data are aligned to the oestradiol peak (day 0).
=

of increased excretion or between the nonpregnant luteal gestation (from the day of observed mating or preovulatory
phases of gonadotrophin-stimulated (247.1 ± 29.9 pg g_I) oestradiol surge to birth) was 94.2 ± 0.5 days (range, 93-96
versus naturally-mated individuals (Fig. 1). Mean duration of days), whereas the duration of the nonpregnant luteal phase
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 Nonpregnant
luteal phase
—
Mated
600 - - 400

-
300

200

100

r—i—r
300

300
200

"5 200
)

loo
-
100 %

lili " " " " —

600 -, 300

400 -
-
200

200 -
100

J
1993 1994
Fig. 2. Representative individual longitudinal profiles of faecal oestradiol ( ) and progestogen (·) metabolite
concentrations in female cheetah at the Phoenix Zoo. Asterisks denote peaks in oestradiol excretion significantly above the
baseline.

was about half (P < 0.05) that of pregnancy (51.2 ± 3.5 days; tors. In females identified as acyclic, faecal monitoring had
range, 38-59 days). been conducted for 90 days or fewer. Two cheetahs (depicted
in Fig. 2b,c) tended to express cyclic activity when the
third female (Fig. 2a) was reproductively inactive (during a
Longitudinal endocrine evaluations nonpregnant luteal phase or anoestrus). The cheetah in Fig.
2a was older (10 years) and was cyclic about 80% of the time
Eighteen of 24 cheetahs (75%) monitored for 60 days or compared with the two younger sibling females (3 years;
more exhibited some evidence of oestrous cyclicity on the Fig. 2b,c), each of which was cyclic about 40% of the
basis of regular fluctuations in oestradiol excretion. In addi¬ time. Similarly, the cheetahs depicted in Fig. 3 also dis¬
tion, all individuals monitored > 1 year (n 7) expressed
=
played periods of anoestrus that were not synchronous. In
cyclic activity, although none were continuously cyclic (Figs the female depicted in Fig. 2c, two pregnancies occurred
2 and 3). Instead, follicular activity was interrupted by within one year. At the end of the first pregnancy, a
anoestrous periods, months in duration, that were
2—5 single cub was born and removed for hand-rearing
neither synchronous among females within facilities nor which resulted in a resumption of ovarian cyclicity within
associated with season or other obvious environmental fac- one week.

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 800 (a) 400

600 300

400 200

Anoestrus Anoestrus
200 ~*- * -<- - 100

> 0

ro
f 800· (b)
o
O Nonpregnant
phase
luteal
Mated
600 600

400 -
400

Nonpregnant
luteal phase
200 200

TT -

1993 1994
Fig. 3. Representative individual longitudinal profiles of faecal oestradiol ( ) and progestogen (·) metabolite
concentrations in female cheetah at the Metro Toronto Zoo. Asterisks denote peaks in oestradiol excretion significantly
above the baseline.

In almost all cases, episodic increases in oestradiol excre¬ Endocrine patterns after ovulation induction and artificial
tion (presumed indicative of oestrus) occurred without a insemination
subsequent rise in progestogen metabolite excretion in non-
mated females (even those housed with other females), In general, oestradiol concentrations increased four- to
indicating a lack of spontaneous ovulation. However, two tenfold after eCG injection (Figs 1 and 5). In the female
females were exceptions, exhibiting significant increases in becoming pregnant after gonadotrophin therapy and artificial
faecal progestogen metabolite concentrations after an oestra¬ insemination, increased progestogen metabolite excretion was
diol surge in the absence of physical contact with a male. sustained throughout the 94 day gestation, although concen¬
Progestogen excretory patterns in these two females were trations fluctuated markedly throughout the luteal period
similar to those observed after induced ovulations, although (Fig. 5a). In one female that failed to conceive, similar
overall concentrations tended to be lower (Fig. 4). In one increases in progestogen metabolite concentrations were
case, increased progestogen excretion was observed within apparent for 57 days after the gonadotrophin-induced
days after the female was relocated to a new enclosure and a oestradiol surge (Fig. 5b). The individual shown in Fig. 5c
male was moved into the adjacent pen on the same day (Fig. had only two distinct follicles > 2 mm in diameter and no
4a). In the other case, the female was translocated and a male corpora lutea at the time of laparoscopy and, based on a lack
introduced into her enclosure one week later. The male of increased progestogen metabolite excretion, ovulation
showed interest in the female (calling, approaches to female), never occurred in response to hCG. A similar anovulatory

but was removed from the enclosure before mounting profile was observed in this female in the subsequent pro¬
occurred (Fig. 4b). cedure for induction of ovulation. The steroid excretory
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 300' (a) 40

Translocation of female
Vocalization by adjacent male
30
200

20

100
-
10
~
-
»

en CJ)
Dl

c
CD
o
V¡ 300 (b) 100
o
Translocation of female
Introduction of male
75
200 -

-
50

25

~~[ " ' I ' I

0 20 40 60
Days from oestradiol peak
Fig. Individual profiles of faecal oestradiol ( ) and progestogen (·) metabolite concentrations in cheetah females at (a)
4.
the White Oak Conservation Center and (b) Wildlife Safari exhibiting spontaneous ovulation (without mounting or
intromission by a male). The female in (a) was relocated to a new enclosure and a male moved into the adjacent enclosure
on the same day. Five days later the male showed interest in the female by vocalizing a 'stutter call'. In (b), the female was

translocated and a male introduced into her enclosure 1 week later. The male showed interest in the female (calling,
approaches to female), but was removed from the enclosure before mounting occurred.

profiles of the remaining individual not conceiving after ovulatory mechanisms (spontaneous versus induced) and
insemination were similar to that depicted in Fig. 5b. steroid profiles during pregnancy 'pseudopregnancy'
versus

(the nonpregnant luteal phase) comprehensively. This

more
information was then used to evaluate possible causes of poor
Discussion reproductive performance in captive cheetahs.
In general, the 13.6 day oestrous cycle determined in
Several studies have used faecal oestradiol and progestogen this study by faecal oestradiol analysis was consistent with
metabolite analyses to examine ovarian activity in cheetahs; the 12-14 day cycle proposed by Eaton and Craig (1973),
however, endocrine assessments were of short duration Bertschinger et al (1984) and Asa et al (1992), based on
( < 90 days) (Brown et al, 1994; Czekala et al, 1994) or based behavioural observations, plasma oestradiol concentrations and
on only a few animals (n = 5, Brown el al, 1994; 7, Czekala
=
vaginal cytology, respectively. Together these data confirm
et al, 1994; 2, Graham et al, 1995). The present study
= that the cheetah is unique among the 'great' cats in exhibiting
evaluated endocrine patterns for extended periods (up to 24 a shorter cycle on average than the approximately 20—30 day

months) in 26 individuals (n 36 total observations, since

=
cycle reported for large felids (lion, Panthera leo, Schmidt et al,
ten females were evaluated twice) to examine seasonality, 1979; puma, Felis concolor, Bonney et al, 1981; tiger, Panthera
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 O CS
ÜO.,
: Al

400 -

400 " 600

oo.,
300 .e Al
-
400

200

100
Aru 200

¿&
1 JftfiWV***0**
' JC- /W,- - » -

-10 10 20 30 40 50 60 70 80 90 100
Days from artificial insemination
Fig. 5. Individual profiles of faecal oestradiol ( ) and progestogen (·) metabolite concentrations in (a) pregnant, (b)
nonpregnant and (c) anovulatory female cheetah subjected to ovulation induction and artificial insemination at the Caldwell
Zoo. Females were injected i.m. with 200 iu eCG followed 80 h later by 100 iu hCG and artificial insemination (AI) 46—48 h
after hCG.

et al, 1985; leopard, Panthera pardas, Schmidt et al,

fi^ris, Seal and Durrant, 1989; Asa et al, 1993; Brown et al, 1995; Graham
1988; snow leopard, Panthera uncia, Schmidt et al, 1993; et al, 1995) and, in part, may be related to the induced
clouded leopard, Neofelis nebulosa, Brown et al, 1995). However ovulatory characteristics of these species. Compared with
even with daily faecal collection, there was considerable spontaneous ovulators, the signalling of oestrus onset and its
variation within and among individuals in oestrous cycle termination in felids appears to be less finely regulated, making
dynamics. Such variability in follicular steroid and behavioural cyclicity more variable.
cycle activity is common within species and members of the During pregnancy, progestogen metabolite concentrations
Felidae (Eaton and Craig, 1973; Kleiman, 1974; Schmidt el al, increased several hundred-fold above baseline values, peaked
1979, 1988, 1993; Bonney el al, 1981; Seal et al, 1985; Yamada about mid-term and then gradually declined until after
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parturition,in a similar way to circulating blood progesterone monomorphism (O'Brien et al, 1983, 1985) and that loss of
concentrations in domestic cats (Schmidt et al, 1983). In mated heterozygosity reduces overall reproductive fitness in other
females that failed to conceive, the duration of the nonpregnant species (Rails et al, 1979; Rails and Ballou, 1983). This reduced
luteal phase was about half that of pregnancy. Except for genetic diversity probably accounts for the extremely high
duration of excretion, however, there were no obvious quali¬ percentage of morphologically abnormal spermatozoa noted in
tative or quantitative differences in progestogen metabolite cheetah electroejaculates (Wildt et al, 1983, 1987; Wildt, 1994).
profiles between pregnant and nonpregnant cheetahs, which is However, poor ejaculate quality and low genetic diversity are
typical of observations in other felids (domestic cat, Shille and observed in both captive cheetahs and in successfully repro¬
Stabenfeldt, 1979; Wildt et al, 1981; lion, Schmidt et al, 1979; ducing free-living cheetahs (O'Brien et al, 1983, 1985; Wildt
Graham et al, 1995; puma, Bonney et al, 1981; leopard, et al, 1987). Thus, genetic factors alone are not likely to be the
Schmidt et al, 1988; snow leopard, Schmidt et al, 1993; major contributors to poor fertility within the captive popula¬
clouded leopard, Brown et al, 1995). Two of 26 cheetahs in the tion. Rather, behavioural problems may be an underlying cause
study population showed evidence of spontaneous (non- of poor reproductive success in cheetahs (Laurenson et al,
mating-induced) ovulations on the basis of increased faecal 1992; Caro, 1993, 1994). Breeding success is associated with
progestogens after an increase in oestradiol. During the repro¬ widely varying husbandry practices and no single method has
ductive survey, Wildt et al (1993) observed no active luteal proven successful across institutions (Caro, 1993). Furthermore,
tissue on the ovaries of nonpregnant or nonlactating females the fact that behavioural signs often are difficult to interpret in
and concluded that cheetahs were induced ovulators. However, cheetahs reinforces the need for integrated studies correlating
distinct luteal scars were found on the ovaries of 12% of behavioural observations with actual endocrine events. The
cheetahs that had never produced young, although mating unexpected finding that animals within the same institution
histories were unknown. In other studies, neither Czekala et al often alternated periods of oestrous cyclicity leads to specula¬
(1994) nor Bertschinger et al (1984) found evidence of non- tion that reproductive suppression may be occurring among
mating-induced ovulations, whereas Asa et al (1992) did some cheetah females housed together or in close proximity.

quantify a sustained increase in serum concentrations of Although not documented within the Felidae (most of which
progesterone in a singleton cheetah. Comparatively, no 'spon¬ are solitary), reproductive suppression of subordinates occurs
taneous' ovulations have been reported in pumas (Bonney in many social species, including callitrichid primates (Abbott,
et al,1981), tigers (Seal et al, 1985) or snow leopards (Schmidt 1984; Epple and Katz, 1984; French et al, 1984), naked
et al,1993), whereas occasional non-mating-induced ovulations mole rats (Heterocephalus glaber, Faulkes et al, 1990), dwarf
have been observed in lions (Schramm et al, 1994) and clouded mongooses (Helogale párvula, Creel el al, 1992) and African
leopards (Brown et al, 1995; Howard et al, in press) maintained wild dogs (Lycaon pictus, Frame et al, 1979; Fuller et al, 1992).
in female groups or as singletons, and in leopard females In the wild, female cheetahs tend to travel alone, whereas males
housed together, but not alone (Schmidt et al, 1988). Taken live in stable coalitions of 2—3 animals (Laurenson et al, 1992;
together, these data demonstrate that, while usually ovulating Caro, 1993, 1994). Keeping males and females together con¬
only after copulation, ovulation in some individual felids can be tinually in captivity or the absence of male coalitions may be
triggered occasionally by physical or psychosocial stimuli detrimental to promoting natural courtship behaviour in both
unrelated to mating. Furthermore, although the incidence of sexes. This finding warrants further investigation using more

spontaneous ovulations may vary among species, for cheetahs controlled experimental procedures.
it appears to be extremely low. It is clear that any meaningful evaluation of reproductive
In the survey of Wildt et al (1993), females demonstrated status in individual female cheetahs requires long-term evalu¬
minimal, if any, ovarian activity at the time of examination. ation of ovarian activity and emphasizes the power of non-
Although about 67% of the surveyed population had at least invasive faecal steroid monitoring for assessing reproductive
one ovarian follicle >2 mm in diameter, only 23% had ovaries activity. From a practical perspective, faecal steroid analyses
containing follicles considered mature ( > 4 mm). Most of these will provide critical information needed for making appropriate
surveyed cheetahs also had low serum oestradiol concen¬ captive management decisions, especially on how environ¬
trations, further suggesting they were reproductively inactive mental changes or husbandry practices affect reproductive
(Wildt et al. 1993). However, this single-point-in-time survey activity. These assays are also an important adjunct tool for
was not designed to evaluate ovarian dynamics. By monitoring
assessing ovarian responses to gonadotrophin therapy, allow¬
longitudinal ovarian steroid excretion, our study found that, ing for subtle improvements that eventually should permit
over prolonged periods, 75% of the cheetahs did exhibit some assisted reproduction to be even more useful for maintaining
follicular activity. In addition, all females examined for a year or genetic diversity within small populations.
more demonstrated waves of follicular activity for as little as
25% and up to 80% of the time. None of this reproductive The authors thank R. Hoyt and T. Volk of the Phoenix Zoo;
activity appeared to be seasonally mediated. It now remains C. Marsh and M. Tucker of the Caldwell Zoo; J. Hausjergen, K. Van
to be determined what mediates this discontinuous ovarian der Molen and T. Vargas of the Sacramento Zoo; J. Fleming,
K. Ziegler and L. Ferguson of the White Oak Conservation Center;
cyclicity in cheetahs and how (or if) it affects overall reproduc¬ T. Peterson, S. Russell and G. Ziegler of the Wildlife Safari; and
tive performance. Several physiological causes were eliminated
A. Bellem, H. Tomaso, W. Rowntree and K. Grieg of the Metro
by the survey of Wildt et al (1993), which reported no Toronto Zoo for logistical support and sample collection. They
differences in reproductive tract anatomy, pituitary function or are also grateful to S. Beekman, K. Terio and A. Moresco for technical

gonadal activity between proven and unproven breeders. It assistance. This study was supported by the Friends of the National
also is known that cheetahs exhibit a high degree of genetic Zoo, the New Opportunities in Animal Health Sciences Center, the
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via free access
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