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4 Animal-appropriate housing of ball pythons (Python regius)
5 — Behavior-based evaluation of two types of housing systems
6
7 Tina Hollandt¹¶, Markus Baur¹&, Caroline Wöhr²&
8
9
10
11 1 Auffangstation für Reptilien München e. V. (Munich Rescue Center for Reptiles), Munich,
12 Germany
13 ² Chair of Animal Welfare, Ethology, Animal Hygiene and Animal Husbandry, Department of
14 Veterinary Sciences, Faculty of Veterinary Medicine, LMU Munich, Munich, Germany
15
16
17 &These authors contributed equally to this work.
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18 Abstract
19 Considering animal welfare, animals should be kept in animal-appropriate and stress-free
20 housing conditions in all circumstances. To assure such conditions, not only basic needs
21 must be met, but also possibilities must be provided that allow animals in captive care to
22 express all species-typical behaviors. Rack housing systems for snakes have become
23 increasingly popular and are widely used; however, from an animal welfare perspective, they
24 are no alternative to furnished terrariums. In this study, we therefore evaluated two types of
25 housing systems for ball pythons (Python regius) by considering the welfare aspect animal
26 behavior. In Part 1 of the study, ball pythons (n = 35) were housed individually in a
27 conventional rack system. The pythons were provided with a hiding place and a water bowl,
28 temperature control was automatic, and the lighting in the room served as indirect
29 illumination. In Part 2 of the study, the same ball pythons, after at least 8 weeks, were
30 housed individually in furnished terrariums. The size of each terrarium was correlated with
31 the body length of each python. The terrariums contained substrate, a hiding place,
32 possibilities for climbing, a water basin for bathing, an elevated basking spot, and living
33 plants. The temperature was controlled automatically, and illumination was provided by a
34 fluorescent tube and a UV lamp. The shown behavior spectrum differed significantly between
35 the two housing systems (p < 0.05). The four behaviors basking, climbing, burrowing, and
36 bathing could only be expressed in the terrarium. Abnormal behaviors that could indicate
37 stereotypies were almost exclusively seen in the rack system. The results show that the
38 housing of ball pythons in a rack system leads to a considerable restriction in species-typical
39 behaviors; thus, the rack system does not meet the requirements for animal-appropriate
40 housing.
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41 Introduction
42 The ball python (Python regius) has been a popular terrarium-housed exotic pet for more
43 than 30 years (DE VOSJOLI 1990). In Europe and North America, it is frequently bred, but
44 also imports of wild snakes or farmed breeds are commercially available. Due to the various
45 breeding goals (coloration, pattern, scaleless skin), the ball python has highly variable
46 phenotypes and thus is still one of the most frequently kept snake species. The international
47 website “www.worldofballpythons.com/morphs/” for the registration of color morphs
48 (accessed on 18 May 2020) lists 7,221 different color shades and patterns. Although the ball
49 python is listed in the Washington Endangered Species Act Appendix II
50 (https://www.cites.org/eng/app/appendices.php, accessed on 18 May 2020) and the German
51 directive VO EG 338/97 Appendix B (https://eur-lex.europa.eu/legal-
52 content/DE/TXT/PDF/?uri=CELEX:01997R0338-20130810, accessed on 18 May 2020), it is
53 exempt from reporting requirements (“Federal Directive on Species Protection”
54 [Bundesartenschutzverordnung] Appendix 5 regarding § 7 Section 2; https://www.gesetze-
55 im-internet.de/bartschv_2005/anlage_5.html, accessed on 18 May 2020); thus, the number
56 of ball pythons kept as pets in Europe and North America is speculative.
57 The ball python is native to West and Central Africa (Nigeria, Uganda, Liberia, Sierra Leone,
58 Guinea, Benin, Ghana, and Togo). It mainly inhabits arid savannas with temperature
59 extremes ranging from 16 to 43 °C (SCHMIDT 1994) and relative humidity ranging from 60%
60 to 95%, with high seasonal variation due to the dry (December to March) and rainy seasons
61 (April to November) (https://www.auswaertiges-amt.de, accessed on 21 April 2020;
62 https://www.iten-online.ch/klima/afrika, accessed on 21 April 2020). The “German Expert
63 Report on Minimum Requirements for the Keeping of Reptiles” (Federal Ministry of Food and
64 Agriculture [Bundesministerium für Ernährung und Landwirtschaft] [BMEL] 1997) stipulates a
65 temperature range of 26–32 °C with a nighttime reduction of 5 °C. A localized heat spot
66 (basking spot) with 38 °C must be provided. During daytime, the ball python often hides in
67 rodent burrows or abandoned termite mounds (SUTHERLAND 2009, SCHMIDT 2009).
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68 These possibilities for hiding offer the snake relatively constant temperature and humidity
69 conditions. At dusk, the ball python leaves its hiding place to forage or fulfil other needs
70 (TRUTNAU 1988, SCHMIDT 1994, KÖLLE 2007). Being a synanthropic species, the ball
71 python is often found near settlements and cultivated fields, where it feeds on rodents (DE
72 VOSJOLI 1990). Due to its body shape, it can be considered a ground-dwelling snake,
73 although it can be seen at low heights on trees, sufficiently robust shrubs, or termite mounds
74 (KÖLLE 2007). Like almost all snakes, the ball python can swim, but its life cycle is not
75 dependent on the presence of water bodies (TRUTNAU 1988). It uses bathing possibilities
76 especially during the molting phase (SCHMIDT 1994).
77 The typical housing system used for pythons is the so-called rack system. It was first
78 designed in North America around 1992 (www.freedombreeder.com/freedom-breeder-rack-
79 systems, accessed on 21 April 2020; REPTIL TV 2014). A rack system is a shelving system
80 with individual bins arranged as drawers. In some models, the bins have individual lids, in
81 other models, they are open on the top and close flush with the upper shelf board. All bins
82 have ventilation holes. Rack systems usually have no lighting elements, so the ambient light
83 provides the only illumination. Heating elements are installed per drawer level, and heating
84 pads or heating cables are most frequently used. The heating elements should be equipped
85 with a thermostat that prevents overheating and undercooling. Racks are available in various
86 sizes. Most importantly, the bins should be flat. Depending on the manufacturers, the
87 synthetic material used for the bins varies from clear acrylic glass to non-transparent plastic.
88 Regarding the bin furnishing, several variants are available. The most used substrate is
89 newspaper, but also rodent litter or bark mulch are used. Most variants include a hiding place
90 and a water bowl (for drinking), in some cases arranged as a bowl with crawl space
91 underneath. Some variants contain additional structural elements such as artificial plants, a
92 water basin (for bathing), or tree branches. Rack housing offers the advantage of quick and
93 complete cleaning, and little space and time are needed to accommodate and maintain many
94 snakes. Because each animal is kept individually, precise animal monitoring is easily
95 possible. Moreover, the sparse furnishing keeps the injury risk low. Further arguments of
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96 breeders and advocators of rack housing can be found in the relevant literature (e.g.,
97 WESTHOFF 2005, McCURLY 2011) and include the following: the animals accept feed more
98 readily in a rack system than in a terrarium; thus, feed refusal occurs less frequently; due to
99 the higher feed intake, the animals grow faster, resulting in a younger breeding age; the
100 animals reproduce more readily; accommodation in the rack system is more natural for the
101 ball python, which in nature lives in termite mounds; the flat design of the bins is thought to
102 cause less stress for the snake (LONGHITANO 2010); animals housed in rack systems are
103 considerably less aggressive (McCURLY 2011). Light causes stress for crepuscular and
104 nocturnal animals—a further argument for indirect or no illumination in the rack drawers.
105 Arguments against rack housing are comprehensively presented in the expert report of
106 Workgroup 8 (Pet Trade and Pet Husbandry) from 19 July 2013; the workgroup comprises
107 members of the “Veterinary Association for Animal Protection” (Tierärztliche Vereinigung für
108 Tierschutz e. V.), the “Federal Association for Expertise on Nature, Animal, and Species
109 Protection” (Bundesverband für fachgerechten Natur-, Tier- und Artenschutz e. V.), the
110 “Workgroup Diseases of Amphibians and Reptiles” (Arbeitsgemeinschaft Amphibien- und
111 Reptilienkrankheiten, a subdivision of the “German Society for Herpetology and
112 Herpetoculture” [Deutsche Gesellschaft für Herpetologie und Terrarienkunde e. V.]), the
113 “German Veterinarian Society” (Deutsche Veterinärmedizinische Gesellschaft e. V. [DVG]),
114 the DVG “Study Group Zoo Animal, Wild Animal, and Exotic Animal Medicine” (DVG
115 Fachgruppe Zootier-, Wildtier- und Exotenmedizin), the DVG “Study Group Pet Birds, Zoo
116 Birds, Wild Birds, Reptiles, and Amphibians” (DVG Fachgruppe Zier-, Zoo- und Wildvögel,
117 Reptilien und Amphibien), and the “Munich Rescue Center for Reptiles” (Auffangstation für
118 Reptilien München e. V.). In the expert report, the workgroup pointed out the lacking
119 possibility for three-dimensional locomotion due to the low height of the rack bins.
120 Furthermore, the small space allowance leaves little room for furnishings, excluding
121 possibilities for hiding in various places (dry, humid, elevated) and for climbing. Depending
122 on the substrate, burrowing may also be impossible. Another concern, not directly addressed
123 in the expert report, is illumination. At the most, rack systems allow illumination via ambient
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124 light or via an LED strip fixed to the lid of the bin. Spotlights, for example with UV light,
125 cannot be installed.
126 In contrast to rack systems, terrariums have been used much longer for housing animals. In
127 1964, the “German Society for Herpetology and Herpetoculture” was founded in Germany
128 (www.dght.de, accessed on 21 April 2020). A terrarium is an enclosure or a container in
129 which various species of animals can be housed (RIECK et al. 2001). The interior climatic
130 conditions are adjusted to the needs of the housed animal species. At least one side of the
131 terrarium is transparent. In contrast to an aquarium, terrestrial elements and air space
132 predominate. Due to the rapid technical developments in almost every area, today’s
133 terraristics is highly progressive. Daytime-dependent variations of temperature, lighting, and
134 humidity can precisely be planned, simulated, and controlled. A skilled use of UV lamps,
135 irrigation systems, and nebulizers in the terrarium allows creating a microclimate that is
136 nearly identical to the microclimate in the natural habitat. In “good terraristics practice,” the
137 animal is provided with various elements for expressing its needs. Climbing possibilities,
138 various hiding places, substrate for burrowing, and plants are included according to the
139 housed animal species. Living plants not only ensure the formation of a natural microclimate
140 but also provide structural change over time. Various types of light sources can be used for
141 illumination. Energy efficient LED bulbs can provide basic illumination. To simulate natural
142 sunlight for the basking spot, UV lamps of appropriate wavelengths and intensity should be
143 selected according to the animal species. Similarly, heating elements should optimally
144 radiate heat like the sun, i.e., from the top to the bottom.
145 Beyond the body of specialized literature, we found a few arguments against housing the ball
146 python in a terrarium (e.g., WESTHOFF 2005, McCURLY 2011), but these arguments are
147 based on observations and have not been analyzed scientifically. According to the “German
148 Expert Report on Minimum Requirements for the Keeping of Reptiles” of 1997, the ball
149 python does not feel safe in a terrarium exceeding a certain height. Because this snake is a
150 ground dweller and not a good climber, a terrarium that is too high poses the risk of the
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151 animal falling and getting injured (WESTHOFF 2005). Furthermore, due to perception of the
152 surrounding environment (e.g., through a glass front), the snake feels threatened and often
153 reacts very aggressively (McCURLY 2011). Lighting additionally stresses the ball python
154 (McCURLY 2011). All these factors can lead to feed refusal, slow growth, and poor
155 reproduction rates in a terrarium. Moreover, growth of health hazardous bacteria and molds
156 often occurs in a terrarium (McCURLY 2011).
157 Many wild animals kept in captivity show stereotypical behaviors. A stereotypy is a repetitive,
158 invariant behavior or movement pattern without function or goal and is often seen due to
159 inadequate husbandry conditions (DÜPPJAN and PUPPE 2016). Therefore, stereotypies are
160 often considered as indicators of impaired wellbeing caused by acute or past suffering. As
161 seen almost exclusively in circumstances of confinement (LANGEN et al. 2011a, 2011b),
162 situations can arise in which an animal is strongly motivated to show a behavior but cannot
163 express it because the necessary circumstances are not given (WECHSLER 1992).
164 Endogenous and exogenous stimuli can induce a readiness to act that is displayed at varying
165 intensity. However, a desire-consuming final action never happens (SAMBRAUS 1982)
166 because the human-made environment does not allow it (FRASER et al. 1997; MORGAN
167 and TROMBORG 2007). Such a conflict situation evokes a coping strategy by which the
168 animal seeks alternative possibilities to cope with a frustrating situation that it can neither
169 avoid nor change. The associated action often begins with aggressive behavior, which is
170 expressed strongly or weakly, depending on the animal species. If this behavior does not
171 change the situation, deprivation develops. If the circumstances continue to remain
172 unchanged, certain stimuli will lead to behavior patterns that have no function or goal. In
173 invariant environmental conditions, these behavior patterns are shown increasingly often and
174 manifest as a stereotypy (WECHSLER 1992). Stereotypies can be divided into two
175 categories. One is referred to as redirected action, whereby a behavior is directed at an
176 inadequate object (e.g., a male tortoise may try to copulate with a shoe). The other category
177 is the so-called vacuum activity, whereby no object is used (e.g., walk stereotypies or, as in
178 the present study, crawl stereotypies). A walk or crawl stereotypy can be based on one of
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179 two functional areas of behavior. The behavior may represent an escape attempt or a search
180 behavior (food, mate, other resources). An escape attempt always indicates a state of
181 arousal along with discomfort and thus a reduced wellbeing (WARWICK et al. 1995).
182 Therefore, the housing environment should be designed in a way that always allows the
183 animals to express their natural behavior repertoire and to cope with all arising challenges
184 (WECHSLER 1995, MASON et al. 2007). Moreover, enriched housing conditions can evoke
185 positive emotions, which cause improved wellbeing and contribute to solving behavioral
186 problems (MASON et al. 2007). The aim of the present study is a scientific, comparative
187 evaluation of ball python husbandry by considering animal welfare aspects when housing
188 these animals in a rack system or a terrarium.
189 Animals, Materials, and Methods
190 Ball python (Python regius)
191 Thirty-five ball pythons (Python regius) were used for this study (see Table 1). Twenty-five of
192 them were male, nine were female, and one was juvenile of undetermined sex. Three of the
193 pythons had been handed in by private persons, whereas the others had been confiscated
194 from five snake keepers by authorized agencies. Thirteen of the pythons were between 3
195 and 18 years old. The age of the other pythons (n = 22) was unknown.
196 Body weight, length, and color
197 At the beginning of this study, the pythons had a body length ranging from 53 to 148 cm and
198 a body weight ranging from 0.11 to 2.50 kg. We did not find a sex-specific length or weight
199 distribution. Approximately half (n = 18) of the snakes had a color or a pattern (or both)
200 divergent from the wild type (see Table 1).
201
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202 Table 1: Characteristics of the studied ball pythons (n = 35)
Animal
number
Sex
Age
(years)
Length
(cm)
Weight (g)
Color/pattern
Origin
1
male
unknown
125
1,570
WT
CA
2
male
unknown
128
1,470
WT
CA
3
male
unknown
100
890
M, Albino
CA
4
female
unknown
104
1,400
WT
CA
5
male
unknown
95
420
M, Albino
CA
6
male
15
115
1,300
WT
PP
7
male
15
110
1,305
WT
PP
8
male
3
100
1,100
M, Albino
CA
9
male
unknown
98
1,000
M, Banana
Spider
CA
10
male
unknown
100
1,190
WT
CA
11
male
unknown
110
970
M, Spider
CA
12
female
unknown
85
630
WT
CA
13
female
3
110
1,400
M, Cinnamon
CA
14
male
unknown
100
1,000
WT
CA
15
female
4
110
1,210
M, Butter
Spider
CA
16
male
5
120
1,580
M, Enchi
CA
17
female
unknown
120
1,330
M, Desert Pin
CA
18
male
4
119
1,830
M, Pewter
Blast
CA
19
female
4
120
1,580
M, Pastel
CA
20
female
7
115
1,530
WT
CA
21
male
unknown
120
1,440
WT
CA
22
male
4
125
1,590
M, Phantom
CA
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Animal
number
Sex
Age
(years)
Length
(cm)
Weight (g)
Color/pattern
Origin
Bumble Bee
23
male
4
100
1,200
M, Pewter
CA
24
male
unknown
105
1,100
M, Spider
CA
25
male
6
130
1,690
M, Yellow
Belly
CA
26
male
unknown
115
1,300
M, Caramel
CA
27
male
unknown
120
1,090
M, Desert
Ghost
CA
28
male
unknown
148
2,530
WT
CA
29
female
unknown
135
2,200
WT
CA
30
male
unknown
110
1,300
WT
CA
31
undetermined
unknown
53
118
WT
PP
32
male
unknown
135
1,654
WT
CA
33
male
18
112
755
WT
CA
34
male
unknown
98
731
M, Pastel
CA
35
female
unknown
110
758
WT
CA
Mean ±
SD
7 ± 5
111.4 ± 16.6
1,233.5 ± 505.4
203 WT = wild type; M = morph; CA = confiscating agency; PP = private person
204
205 Feeding
206 In feeding intervals of 2 weeks, the snakes were offered defrosted mice (Mus musculus)
207 warmed up to body temperature. The juvenile snake (No. 31) received “hoppers” (subadult
208 mice), the adult snakes received adult mice, and the largest snakes received subadult rats
209 (Rattus rattus). The numbers and sizes of the feeder animals were tailored to each snake
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210 based on personal experience. Seventeen pythons ate dead mice from the first feeding
211 onward, whereas eighteen pythons refused to eat dead feeder animals despite multiple
212 offerings during various daytimes and with simulation of prey movement. Therefore, these
213 pythons were offered living mice from the third feeding onward, and five of them began
214 eating. From the sixth feeding onward, living multimammate mice (Mastomys coucha) and
215 living rats were offered. Seven snakes that had not accepted feed until then ate these feeder
216 animals, but another six feed-refusing pythons did not. Because young, small guinea pigs
217 (Cavia porcellus) were not available, defrosted mice were covered with pieces of guinea pig
218 fur. With this method, all feed-refusing snakes finally ate. This specialization on only one
219 species of feeder animal was due to the previous husbandry conditions in which the snakes
220 were mostly fed newborn guinea pigs (source: confiscating agency).
221 Housing systems
222 For the present study, the pythons were kept in two types of housing systems. First, they
223 were housed in a rack system. Afterwards, they were housed in terrariums.
224 Housing in the rack system
225 The rack system consisted of clear acrylic polypropylene bins (70 × 40 x 16 cm LWH) with
226 ventilation holes in the front and back sides (see Figures 1 and 2). The bins were placed
227 precisely fitted as drawers in a shelving system consisting of a non-transparent plastic frame
228 and boards made of oriented strand board. The back half of the bin was heated with a
229 heating cable and pad, controlled via a thermostat (Thermo Control Pro II, Lucky Reptile).
230 The daytime temperature from 8:00 a.m. to 8:00 p.m. was on average 28 °C (26–32 °C) at
231 the back end measured above the heater element and on average 26 °C (27–30 °C) at the
232 front end of the bin. In the time from 8:01 p.m. to 7:59 a.m., the temperature at each end was
233 3 °C less. The bottom was covered with newspaper. An upside-down plastic plant pot of
234 27 cm diameter with an entrance hole of 8 cm diameter served as hiding place. During the
235 molting period, moist towels were put inside the hiding place. Fresh water was provided ad
236 libitum in a bowl that was fixed to the bottom and one side of the bin with a hook-and-loop
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237 fastening strap. For the nighttime observation, one side of each drawer had a hole of 0.5 cm
238 diameter, which allowed illuminating the drawer with red light (LED 650 nm). This wavelength
239 lies outside the visible spectrum of the ball python (SILLMAN 1999).
240
241 Figure 1: Schematic view of a rack drawer
242 Figure 2: Photo of a rack drawer
243
244 Housing in the terrarium
245 For housing the pythons in a terrarium (see Figures 3 and 4), three sizes of terrariums were
246 used. They met the minimum requirements for housing reptiles (BMEL 1997). The smallest
247 terrariums measured 100 × 50 × 50 cm (LWH, Size 1), the medium-sized 120 × 60 × 60 cm
248 (Size 2), and the largest 150 × 80 × 80 cm (Size 3). Basic illumination in all terrariums was
249 provided via a fluorescent tube (Osram 865, 6500 Kelvin; Size 1: 18 W, Size 2: 30 W, Size 3:
250 36 W). For protection, the tube was installed in a moisture-proof bracket. As spotlight, we
251 used a UV lamp (Size 1: Lucky Reptile Bright Sun UV Jungle 35 W, 34 cm above the basking
252 platform; Sizes 2 and 3: Lucky Reptile Bright Sun UV Jungle 50 W, 39 cm above the basking
253 platform) in a protective wire case (Lucky Reptile Thermo Socket plus Reflector). The
254 temperatures during daytime (8:00 a.m. to 8:00 p.m.) were 38 °C underneath the spotlight
255 and 25 °C in the coolest area. During nighttime, the measured temperature was on average
256 24 °C (22–26 °C). The substrate was a mixture of soil (60%), sand (20%), bark mulch (15%),
257 and loam powder (5%). In the back half, the substrate was raised to a height of 35 cm to
258 enable the snakes to burrow. The average substrate thickness in the front half was 10 cm.
259 Each terrarium had a hiding place like the one used in the rack system and an elevated
260 basking platform underneath the UV lamp. Furthermore, each terrarium contained a water
261 basin and a living plant, which was held in place by a layer of gravel. The remaining
262 furnishings included trunks, branches, twigs, clumps of grass, roots, moss, rocks, and bark
263 and had been collected outdoors. The arrangement of the furnishings was identical, but the
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264 use of natural materials did not allow a 100% match. For video recordings, each terrarium
265 was illuminated with a single red LED bulb (650 nm) that was controlled with a timer.
266
267 Figure 3: Schematic view of a terrarium
268
269 Figure 4: Photo of a terrarium (Size 1)
270
271 Behavior observation
272 All pythons were observed in the rack system and the terrarium. In the rack system, a
273 camera (Qumox SJ 4000) was installed at the front end of the drawer and turned on for five
274 consecutive days. All lights on the camera were covered with tape so that only the red light
275 from the LED bulb (nighttime) and the ambient lighting in the room served as light sources.
276 To allow an adaptation period, the camera was installed on the rack 5 days before the
277 recording. The behavior observation began at 5:00 p.m. for 24 hours. The nighttime
278 observation in the terrarium was also facilitated by red LED illumination. For practical
279 reasons, the daytime observation was done without camera, although the switched-off
280 camera remained in the terrarium. Because an ethogram for ball pythons did not exist, we
281 created one based on the observations (see Table 2). It does not include interactions with
282 other individuals because all pythons were single housed during the whole study. Feeding
283 behavior is also excluded because feeding was a planned event that the individual could not
284 control.
285
286 Table 2: Ethogram for the ball python
Behavior
Abbreviation
Locomotion
L
1. Crawling forward
L1
2. Moving backward
L2
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3. Lifting the front body up
L3
4. Climbing
L4
5. Burrowing
L5
6. Moving the head
L6
Exploration behavior directed at the camera
E
Comfort behavior
C
1. Basking
C1
2. Bathing
C2
3. Resting in the hiding place with side wall contact
C3
4. Resting outside of the hiding place, not under the basking spot,
coiled
C4
5. Resting outside of the hiding place, not under the basking spot,
stretched out
C5
Defensive behavior, aggressive behavior
A
Feeding behavior: drinking
F
Other behaviors
O
1. Yawning
O1
2. Pushing the mouth against a barrier (side walls, top)
O2
3. Pathological behaviors (wobbling, stargazing)
O3
287
288 Locomotion
289 Behaviors were classified as locomotion when none of the other behaviors listed in Table 2
290 additionally occurred. “Crawling forward” includes lateral undulation, retilinear locomotion,
291 and a combination of both. “Moving backward” refers to movements of the whole body or of
292 body parts. True backward crawling is not possible due to the scales, so the movement is a
293 pushing motion facilitated by partial or complete lifting of the body. “Climbing” includes all
294 movements during which at least half of the body does not touch the ground. “Burrowing” is
295 an activity during which at least the head up to the eyes is burrowed in the substrate.
296 Movements that include only the head were assessed separately.
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297 Exploration behavior directed at the camera
298 This behavior means that the snake approaches the camera, touches it with its mouth, and
299 probes it with its tongue.
300 Comfort behavior
301 Comfort behavior includes behaviors that often accompany resting behavior. “Basking” is the
302 active visiting and staying at the basking spot, without differentiation of body positions.
303 “Bathing” describes an active visiting of the water basin and lying in the water. Crawling
304 through the water basin is not counted as bathing. “Resting in the hiding place with side wall
305 contact” can be viewed as resting behavior. Lying outside of the hiding place, either coiled or
306 stretched out, is a resting behavior and furthermore indicates a level of comfort in the snake
307 because this behavior does not offer protection, in contrast to lying inside the hiding pace.
308 Defensive behavior
309 Defensive behavior in most cases is a sequence of behaviors. The python moves its front
310 body into S-shaped loops and afterwards may vocalize by making a loud hissing sound. A
311 defensive bite can occur with the mouth closed or open. All these behaviors were also
312 recorded when they occurred individually.
313 Feeding behavior
314 The ethogram lists only “drinking” because the snakes could not control the timing of feeding.
315 During drinking, the mouth (and sometimes the head up to the eyes) is submerged under the
316 water surface in the water bowl, and water is sucked in through chewing movements.
317 Other behaviors
318 “Other behaviors,” in contrast to the above-described ones, are not interconnected.
319 “Yawning” is often seen after feeding but can also occur spontaneously. Another typical
320 behavior is the crawling alongside the barriers of the enclosure whilst “pushing the mouth
321 against side walls or the top.” The pushing could be a soft touching, but it could also be
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322 strong enough to lead to temporary deformation of the mouth. “Wobbling” and “stargazing”
323 are abnormal behaviors that mostly occur in certain color morphs (e.g., Spider) or with the
324 onset of disease (e.g., arenavirus infection). They describe a disoriented, vibrating
325 movement with spiraling turns or crawling on the back. These movements are often
326 associated with a stimulus, such as the offering of feed.
327 Ethics statement
328 Before the beginning of this study, the study design was submitted to the ethics committee of
329 the Center for Clinical Veterinary Medicine, Faculty of Veterinary Medicine, LMU Munich,
330 Germany. The study was approved under protocol number 99-20-10-2017.
331 Behavior assessments
332 The behaviors were documented in 10-min intervals, resulting in a dataset of 144 behavior
333 units per day. This assessment was done on 5 days for each housing system. For
334 comparative data analysis, the area under the curve (AUC) was calculated. For a more
335 precise comparison of behavior rhythms in the two housing systems, we divided the day in
336 three periods. The presumed main activity phase (Period 1; P1) from late afternoon to early
337 night was between 4:00 p.m. and 11:00 p.m.; it was followed by the nighttime phase
338 (Period 2; P2) until 7:00 a.m. the next day and then the daytime phase (Period 3; P3) until
339 dusk (3:59 p.m.).
340
341 Statistical analysis
342 The collected data were first transcribed in Microsoft Excel 2007 (Microsoft Corporation,
343 Redmond, CA, USA). For statistical analysis, we used IBM SPPS Statistics (IBM
344 Deutschland GmbH, Ehningen, Germany) and MedCalc (MedCalc Software Ltd, Ostend,
345 Belgium). Differences between the housing systems in the frequency of shown behaviors
346 were determined with the t-test. Differences between the daytime periods within and between
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347 the housing systems were analyzed with the t-test and the Wilcoxon test. The level of
348 significance was set at p < 0.05.
349 Results
350 In this study, we differentiated 17 behaviors (see Table 2). Defensive or aggressive behavior
351 (A) was never shown, nor was “moving backward” (L2). “Moving the head” (L6) was never
352 shown as a separate movement but could be observed associated with other behavior
353 components. Table 3 lists the relative frequency of all behaviors displayed in a 24-hour
354 period in the rack system and the terrarium.
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355 Table 3: Comparison of the relative frequency of all behaviors displayed in 24 hours in the
356 two housing systems (rack system and terrarium)
Behavior
Rack system (%)
Terrarium (%)
Crawling forward (L1)
7.11 ± 0.25
15.90 ± 0.02
Lifting the front body up (L3)
0.78 ± 0.006
1.15 ± 0.005
Climbing (L4)
0
7.00 ± 0.02
Burrowing (L5)
0
1.17 ± 0.01
Exploration behavior directed at the camera
(E)
0.55 ± 0.005
0
Basking (C1)
0
9.90 ± 0.05
Bathing (C2)
0
0.90 ± 0.01
Resting inside the hiding place (C3)
53.90 ± 0.15
33.33 ± 0.13
Resting outside of the hiding place, coiled
(C4)
11.24 ± 0.08
11.85 ± 0.07
Resting outside of the hiding place,
stretched out (C5)
14.64 ± 0.09
18.64 ± 0.10
Drinking (F)
0.03 ± 0.0006
0.07 ± 0.0009
Yawning (O1)
0.02 ± 0.0004
0.02 ± 0.0004
Pushing the mouth against a barrier (O2)
11.59 ± 0.02
0.04 ± 0.001
Pathological behaviors (O3)
0.12 ± 0.004
0.03 ± 0.001
357
358 For eight behaviors, we found a statistically significant (p < 0.05) difference between the
359 housing systems. The behavior “crawling forward” (L1) was the most frequent locomotion
360 behavior in both housing systems. It occurred significantly (p < 0.05) more often in the
361 terrarium (AUC = 21.6) than in the rack system (AUC = 9.7). “Pushing the mouth against a
362 barrier” (O2) occurred significantly (p < 0.05) more often in the rack system (AUC = 15.9)
363 than in the terrarium (AUC = 0.1). The pythons spent a large part of the day resting (C3–C5).
364 “Resting in the hiding place” (C3) was the most frequent variant and occurred significantly
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365 (p < 0.05) more often in the rack system (AUC = 79.6) than in the terrarium (AUC = 50.9).
366 “Basking” under the UV lamp (C1), “climbing” (L4), and “bathing” (C2) occurred only in the
367 terrarium. These behaviors could not occur in the rack system because of its structural
368 design. “Exploration behavior directed at the camera” (E), although possible in the terrarium,
369 was shown only in the rack system (AUC = 0.9).
370 We also found daytime-specific differences within and between the housing systems. In the
371 following, P1 refers to the main activity phase from 4:00 p.m. to 11:00 p.m., P2 to the
372 nighttime phase from 11:01 p.m. to 7:00 a.m., and P3 to the early daytime phase from
373 7:01 a.m. to 3:59 p.m
374 In the terrarium, the behavior “crawling forward” (L1; see Figure 5) was shown most
375 frequently during P1 (AUC = 38.0) and considerably less during P2 (AUC = 5.8) and P3
376 (AUC = 6.9). During all periods, the values differed significantly (p < 0.0035) from those in
377 the rack system (P1: AUC = 16.0; P2: AUC = 3.1; P3: AUC = 2.3). In addition, the differences
378 between the periods were considerably smaller in the rack system than in the terrarium.
379
380 Figure 5: Boxplot with extreme outliers (*).Frequency of the locomotion behavior “crawling
381 forward” (L1) during the three daytime periods (P) depending on the two housing systems
382 (p < 0.05).
383
384 During all periods, “lifting the front body up” (L3) was observed similarly often in both housing
385 systems. This behavior occurred most frequently during P1, both in the rack system
386 (AUC = 0.5) and in the terrarium (AUC = 5.8). During the other two periods, it occurred less
387 often in both housing systems (AUC = 0.4 ± 0.1).
388 “Climbing” (L4) behavior in the terrarium also had its activity peak during P1 (AUC = 14.5)
389 and occurred considerably less often during the other two periods (P2: AUC = 2.6; P3:
390 AUC = 3.4). We made similar observations (see Figure 6) for the other three behaviors that
391 could only be shown in the terrarium. “Burrowing” (L5) occurred most frequently during P1
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392 (AUC = 3.9), followed by P2 (AUC = 0.7) and P3 (AUC = 0.2). “Bathing” (C2) was observed
393 most frequently during P1 (AUC = 2.1), much less during P3 (AUC = 1.0), and not at all
394 during the nighttime period (P2). Because of the set lighting intervals, “basking” (C1) could
395 occur only during P1 (AUC = 14.7) and P3 (AUC = 10.8). The three albinotic ball pythons
396 were basking for on average 10 ± 2 min/day, much less than the other ball pythons, which
397 were basking for on average 144 ± 13 min/day.
398
399 Figure 6: Occurrence of four behaviors in the terrarium during the three daytime periods (P)
400
401 “Exploration behavior directed at the camera” (E) in the rack system occurred most
402 frequently during P1 (AUC = 0.9) and rarely during the other two periods (P2: AUC = 0.2; P3:
403 AUC = 0.1). It did not occur in the terrarium.
404 “Resting in the hiding place” (C3; see Figure 7) was most frequently observed during P1
405 (rack system: AUC = 63.8; terrarium: AUC = 36.4). During the other periods (P2 and P3
406 combined), it occurred at similar frequencies within each housing system (rack system:
407 AUC = 29 ± 7; terrarium: AUC = 18.2 ± 1.3).
408
409 Figure 7: Boxplot with outliers (°).Frequency of the comfort behavior “resting in the hiding
410 place” (C3) during the three daytime periods (P) depending on the two housing systems
411 (p < 0.05)
412
413 “Coiled resting outside of the hiding place” (C4; see Figure 8) was shown at similar
414 frequencies in both housing systems during all daytime periods. We found a small behavior
415 peak during P1 in both the rack system (AUC = 13.4) and the terrarium (AUC = 9.3). During
416 the other two periods, this comfort behavior occurred at almost identical frequencies within
417 each housing system (rack system: AUC = 6.2 ± 0.1; terrarium: AUC = 5.45 ± 0.45).
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418
419 Figure 8: Boxplot with outlier (°) and extreme outliers (*).Frequency of the comfort behavior
420 “resting outside of the hiding place, coiled” (C4) during the three daytime periods (P)
421 depending on the two housing systems (p > 37.92)
422
423 By contrast, “stretched-out resting outside of the hiding place” (C5; see Figure 9) in the
424 terrarium was observed more frequently during the activity phase (P1: AUC = 18.9) and the
425 nighttime phase (P2: AUC = 14.6) and less frequently during the early day (P3: AUC = 5.6).
426 The frequency of this comfort behavior in the rack system during P1 and P2
427 (AUC = 11.6 ± 2.6) was also higher than during P3 (AUC = 5.6).
428
429 Figure 9: Boxplot with outliers (°) and extreme outliers (*).Frequency of the comfort behavior
430 “resting outside of the hiding place, stretched out” (C5) during the three daytime periods (P)
431 depending on the two housing systems (p > 24.38)
432
433 We found a considerable difference between the two housing systems for the behavior
434 “pushing the mouth against a barrier” (O2; see Figure 10). The pythons showed this behavior
435 significantly more often (p < 0.05) and almost exclusively in the rack system. In the rack
436 system, we furthermore observed a significant difference (p < 0.05) in this behavior between
437 P1 (AUC = 33.6) and the other two periods (AUC = 4.0 ± 1.9).
438
439 Figure 10: Boxplot with outliers (°).Frequency of the behavior “pushing the mouth against a
440 barrier” (O2) during the three daytime periods (P) depending on the two housing systems
441 (p < 0.05)
442
443 A difference in “drinking” (F), “yawning” (O1), or „pathological behaviors” (O3) was not
444 observed. The pythons showed all three behaviors sporadically during all daytime periods
445 and in both housing systems.
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446 Discussion
447 This work compared the behavior of ball pythons in two types of housing systems, namely, a
448 rack system and a terrarium. We found significant differences in the assessed behaviors
449 depending on the housing system. The pythons in this study showed several often-
450 underestimated behaviors (basking, climbing, bathing, burrowing), indicating the necessity
451 for a new definition of animal-appropriate husbandry of the ball python. Although the results
452 showed that the pythons spent most of the day resting (in the rack system: 80%, in the
453 terrarium 64% of a 24-hour day), the way in which they rested differed between terrarium and
454 rack system. Especially the stretched-out resting outside of the hiding place tended to occur
455 more frequently in the terrarium. During the remaining time, the snakes also showed different
456 frequencies in the assessed behaviors depending on the housing system.
457 Locomotion behaviors such as climbing and burrowing were exclusively shown in the
458 terrarium; they could not be expressed in the rack system due to spatial and structural
459 conditions. The ball python is considered a ground-dwelling snake (SCHMIDT 1994).
460 However, it may occasionally crawl onto a termite mound or climb within waist-high branch
461 wood. An animal-appropriate accommodation must therefore enable the snake to move in
462 three-dimensional space. Burrowing and bathing were shown less often, but they are
463 important components of the behavioral repertoire and must be facilitated for the ball python.
464 Although bathing, a type of comfort behavior, plays only a minor role in the natural behavior
465 of the ball python, this snake species has access to water in its natural habitat. Therefore, a
466 large enough water basin should be provided in a housing system.
467 Many authors (e.g., McCURLY 2011) believe that snakes do not need UV light to stay
468 healthy. However, the behavior of the herein studied pythons clearly showed that UV light is
469 necessary for an animal-appropriate environment that meets the needs of a ball python. The
470 pythons actively visited the basking spot and used it daily for on average 144 min. In a
471 preliminary study, we had found that basking spots without UV light were used significantly
472 less than basking spots with UV light. Most ball pythons have a daily rhythm, in which they
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473 crawl to the basking spot when the light is switched on and stay there to warm up. This
474 phase of warming up is followed by a phase of activity, which is followed by a phase of
475 resting. Before the UV light is switched off, the snakes revisit the basking spot to warm up
476 before dusk, when their phase of main activity begins. This natural rhythm clearly shows how
477 the breeding of color morphs (e.g., Albino) can restrict normal behaviors. Due to their
478 heightened light sensitivity, the albinotic pythons in our study visited the basking spot under
479 UV light less often and for much shorter duration (daily average: 10 min) than the pigmented
480 pythons did. Because basking, with approx. 10% of the 12-hour light period, made up a large
481 share in the behavior repertoire of the ball python, the question arises in how far the selective
482 breeding of albinotic morphs represents cases of so-called torture breeding in terms of the
483 German Animal Welfare Act (§ 11b, German Animal Welfare Act as promulgated on 18 May
484 2006 [BGBl. I S. 1206, 1313], last amended by Article 101 of the act on 20 November 2019
485 [BGBl. I S. 1626]).
486 The pythons showed an excessive interest in the camera only when they were housed in the
487 rack system. This finding indicates that the ball python accepts any stimulus to express
488 exploration behavior. Furthermore, it might explain why ball pythons easily feed and
489 reproduce in a rack system. However, it is no evidence of animal-appropriate housing but
490 simply indicates that the snakes use every opportunity to compensate for the lack of stimuli.
491 In a furnished environment with many stimuli, an individual new stimulus that neither meets a
492 basic need nor poses a clear advantage or disadvantage for the animal does not elicit
493 interest.
494 In the present study, non-species-typical behavior occurred significantly more frequently
495 (p < 0.05) in the rack system than in the terrarium. In rack housing, 12% of all shown
496 behaviors were stereotypical movements, in terrarium housing, the respective frequency was
497 less than 0.04%. The snakes crawled alongside the entire rack drawer and pushed their
498 mouth against the sides (mostly the upper edges) and partially against the top. Several of the
499 pythons (n = 10) stuck their nose through the ventilation holes and tried to widen them
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500 through burrowing movements. Because all pythons stopped showing this “mouth pushing”
501 behavior as soon as they were transferred to a terrarium, this behavior cannot be considered
502 a classical stereotypy, in which the behavior would be continued despite the change in
503 circumstances (MASON and LATHAM 2004). However, during the rack housing period, we
504 observed individual differences. Several pythons (n = 9) showed the above-described “mouth
505 pushing” behavior on the first day of rack housing but then entered a resting state. Others
506 (n = 16) initially showed a resting phase of several days, but once they started showing the
507 “mouth pushing” behavior, they did not stop showing it for the remaining rack housing period.
508 The remaining pythons (n = 10) did not show a specific pattern in the “mouth pushing”
509 behavior. We could not find a link to any other assessed parameter. By contrast, the
510 pathological behavior “wobbling” was not shown depending on the housing type but was
511 exclusively shown by the color morph Spider and those resembling it (n = 5). Presumably,
512 due to a deformation of the inner ear, these morphs have difficulties keeping their balance,
513 especially in states of arousal (SCHRENK et al. 2019).
514 The non-occurrence of defensive behavior in our study may be explained by the lack of a
515 stimulus (predator, disturbance). The same applies to backward movement, which usually is
516 observed when snakes are threatened and keep their gaze on the source of the threat while
517 they retreat. In the present study, a threat stimulus was not given.
518 In summary, our study results show that based on the assessed aspects, the housing in a
519 rack system cannot be considered an animal-appropriate accommodation for the ball python.
520 The only animal-based advantage of rack housing is the possibility for complete and fast
521 cleaning. This aspect can be useful for keeping sick animals or facilitating quarantine
522 conditions. Further aspects such as the keeping of many animals in small spaces or the time-
523 saving maintenance of these animals are in no case in the interest of the snakes. These
524 conditions are rather reminiscent of intensive mass husbandry, in which economic aspects
525 are considered to be of higher priority than animal welfare.
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526 Our results do not support the argument that the ball python accepts feed more readily in a
527 rack system than in a terrarium. With the rack system, we initially encountered difficulties in
528 feed acceptance, but these were most likely due to the kind of offered feed. Because the
529 snakes in both housing systems did not differ in their readiness to eat, the reason for
530 previously reported higher growth rate in the rack system (McCURLY 2011) is most likely a
531 lower calory use due to reduced locomotion. Crawling forward alone made up 15% (on
532 average) of all shown behaviors in the terrarium. In the rack system, the share of this
533 locomotion behavior was only 7%. Moreover, other calory-burning activities such as
534 burrowing and climbing occurred only in the terrarium. These results suggest that the ball
535 pythons used less energy for locomotion in the rack system and thus could invest excess
536 calories in growth. Snakes that move little have a reduced muscle mass and tonus, as
537 compared with snakes that can express their full behavior repertoire. Due to the reduced
538 muscle tonus, the snakes are less able to keep their body in certain positions. A ball python
539 that has the possibility to express all physiological movements because it lives in a furnished
540 environment can be assumed to have stronger muscles than a ball python that lives in an
541 unstructured and spatially restricted environment.
542 The statement of McCURLEY (2011) that illumination is a stressor for ball pythons could be
543 disproved in our study. If light had caused stress in the snakes, they would not have exposed
544 themselves to it because they always had the possibility to seek shelter in a hiding place.
545 Even the albinotic pythons, for which the duration (on average 10 min/day) of basking
546 differed considerably from that of the pigmented pythons (on average 144 min/day), used the
547 offered light source. For albinotic pythons, a UV lamp of low intensity should be installed.
548 Housing with indirect illumination or in complete darkness is animal-welfare-adverse and thus
549 not acceptable. Darkness would amplify the scarcity of stimuli in the rack system.
550 A terrarium must be adapted to the needs of the housed individual. For instance, the need for
551 protection in juvenile snakes should be met with multiple hiding places and many structural
552 elements, such as dense vegetation. The terrarium dimensions alone cannot be used to
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553 determine if a terrarium is appropriate for housing a ball python. An unstructured, large
554 terrarium in which the animal-appropriate needs are not met is not acceptable. The terrarium
555 should contain several hiding places, possibilities for climbing, substrate for burrowing, a
556 large enough water basin that the snake can use for bathing, and a basking spot with UV
557 light. The natural needs of the ball python are known and thus must be met.
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