1 Association between reproduction and immunity in Herpestes ichneumon is sex- 1
biased and unaffected by body condition 2
3
Bandeira, V.1*, Virgós, E.2, Azevedo, A.3,4, Cunha, M.V.5,6 & Fonseca, C.1 4
This is the accepted version of the article with the final citation:
5
Bandeira, V., E. Virgós,.A. Azevedo, M.V. Cunha & C. Fonseca (2021). Association 6
between reproduction and immunity in the Egyptian mongoose Herpestes ichneumon is 7
sex‐biased and unaffected by body condition. Journal of Zoology 313(2): 124-134. DOI:
8
https://doi.org/10.1111/jzo.12842 9
10
1 Department of Biology & CESAM, University of Aveiro, Campus Universitário de 11
Santiago, 3810-193 Aveiro, Portugal 12
2 Departamento de Biología, Geología, Física y Química Inorgánica. Área 13
Biodiversidad y Conservación, ESCET, Universidad Rey Juan Carlos, c/ Tulipán, s/n., 14
E-28933 Móstoles (Madrid), Spain 15
3 Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Straße 17, 10315 16
Berlin, Germany 17
4 Instituto de Ciências Biomédicas Abel Salazar, R. Jorge de Viterbo Ferreira 228, 18
4050-313 Porto, Portugal 19
5 cE3c- Centre for Ecology, Evolution and Environmental Changes, Faculdade de 20
Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal 21
6 BioISI- Biosystems & Integrative Sciences Institute, Faculdade de Ciências, 22
Universidade de Lisboa, 1749-016 Lisboa, Portugal 23
24
* Corresponding author 25
2 Victor Bandeira
26
Department of Biology & CESAM, University of Aveiro 27
Campus Universitário de Santiago, 28
3810-193 Aveiro 29
Portugal 30
Telephone: +351 234 370 350; Fax: + 351 234 372 587 31
e-mail: victor.bandeira@ua.pt 32
Orcid id: 0000-0002-2181-3372 33
34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
3 Abstract
51 52
The Egyptian mongoose (Herpestes ichneumon) is a carnivore in expansion on the 53
western limits of Europe, where its reproductive ecology is unknown.
54
In this study, we weighed and measured the gonads of 507 wild-caught mongooses 55
ranging its geographical distribution and all seasons of the year. Based on the variation 56
in gonad weight, we determined periods of reproductive activity for females (December 57
to June) and males (throughout the year), with both sexes showing a peak in gonad 58
weight during February. We also identified periods of lactation (March to August, 59
n=10), gestation (December to July, n=20) and mean litter size (1 to 4 offspring, 2.75 ± 60
0.79, n=20).
61
Next, we constructed two separate models to explain the variation in ovarian and 62
testicular weight, using age cohort, season and region, spleen weight, body condition, 63
and the environmental variables habitat, river network and Egyptian mongoose density 64
as predictors. Ovarian weight was influenced by season and spleen weight. Females 65
with heavier ovaries were found in spring and simultaneously exhibited heavier spleens.
66
Testicular weight was influenced by season, spleen weight and age, as well as several 67
environmental variables. Males with lower spleen weight exhibited heavier testes, 68
indicating a male-specific negative association between reproductive and immune 69
activity.
70
Overall, the results of this study refine our knowledge on Egyptian mongoose 71
reproductive ecology. They indicate that reproduction timing is determined by females, 72
whose breeding is seasonal but who are unaffected by the set of environmental variables 73
we tested, as opposed to males, who are influenced by these environmental conditions 74
4 and seem to be reproductively active year-round. These results also support a negative 75
reproduction-immunity trade-off in males, that is independent of body condition and 76
absent in females.
77 78
79
Keywords 80
Egyptian mongoose, Herpestes ichneumon, ovarian weight, Portugal, reproduction, 81
testes weight, trade-off 82
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5 1. Introduction
96 97
Reproductive ecology is a key element of the natural history of all species that directly 98
influences the contribution to the gene pool of the next generation (fitness) through the 99
differential reproduction of individuals (Speakman, 2008). Reproduction can be 100
influenced by factors related to individual traits such as size, body condition or health 101
(Isaac, 2005; Skibiel et al., 2013) and by environmental conditions (Bronson, 2009).
102
Reproduction and survival require energy investments that may place the two processes 103
in competition with each other (Lochmiller & Deerenberg, 2000). Allocation of energy 104
to reproduction can hinder immune function for self-protection (Zuk & Stoehr, 2002;
105
Stoehr & Kokko, 2006; French et al., 2007) and ultimately survival and therefore 106
lifetime reproduction. Inversely, increased energy demand by the immune system 107
caused by disease or parasitism may reduce reproductive performance (Zuk & Stoehr, 108
2002; Stoehr & Kokko, 2006). Therefore, immune-reproductive trade-offs can be very 109
different within and among populations. The study of these trade-offs requires a 110
representative sample of the population, which should ideally include data from its 111
entire geographic distribution, from both sexes and all ages, and a broad range of 112
environmental conditions. However, such studies are lacking for most species.
113
The Egyptian mongoose (Herpestes ichneumon Linnaeus, 1758) is a medium-sized 114
carnivore whose geographic distribution in Europe is confined to the western part of the 115
Iberian Peninsula (Cabral et al., 2005; Do Linh San et al., 2016). Its range has been 116
expanding in recent years towards the north and west (Talegón & Parody, 2009; Recio 117
& Virgós, 2010; Barros & Fonseca, 2011; Balmori & Carbonell, 2012; Barros et al., 118
2015). Currently, this species is legally hunted in Portugal, resulting in a large number 119
of specimens of both sexes throughout the year. Additionally, it is a polygynic species 120
6 (Palomares, 1993a), exhibiting differential investment in reproduction (Palomares, 121
1993a; Palomares & Delibes, 1993b), which makes it a suitable species for studies in 122
reproductive ecology. Currently, there are no studies addressing the reproductive 123
ecology of Herpestes ichneumon in Portugal, or the influence exerted by factors 124
presumed to affect reproductive traits. In Spain, studies are also limited, and consist of 125
longitudinal observations with small numbers of radio-tracked individuals yielding 126
information on periods of copulations, births, pregnancies and litter size (Palomares &
127
Delibes, 1992) and male behaviour and mating tactics (Palomares, 1993a). In Israel, a 128
study based on a small sample of individuals focused on Herpestes ichneumon ecology 129
in different environmental conditions from those found in the Iberian Peninsula (Ben- 130
Yaacov & Yom-Tov, 1983). Reproduction in the Herpestes gender was studied in small 131
Indian mongoose (H. auropunctatus) (Soares & Hoffmann, 1981; Soares & Hoffmann, 132
1982; Hoffmann et al., 1984) and in Javan mongoose (H. javanicus) (Abe et al., 2006) 133
both in islands.
134
In this study, we determined if there are sex-specific conflicts in resource allocation 135
between reproduction and immunity in the Egyptian mongoose. For that purpose, we 136
first investigated reproductive traits across the complete range of environmental 137
conditions that the species can experience in its European distribution, determining litter 138
sizes and the timing of pregnancy and lactation. Secondly, we investigated whether and 139
how indicators of immunity (spleen weight) and of energy availability (body condition) 140
relate to the weight of reproductive organs in each sex, age cohort, season and region, 141
under different environmental, climatic and ecological pressures. We predicted that, in 142
presence of an immunity-reproduction trade-off, an increase in spleen weight would be 143
negatively associated with the weight of reproductive organs. Additionally, we expected 144
such negative correlation to become more evident when energy is scarce, i.e. with the 145
7 decrease in body condition. However, in recent work, we observed that Egyptian 146
mongoose’s spleen weight varies between sexes and increases during spring, coinciding 147
with the highest moment of investment in reproduction, and was unaffected by body 148
condition (Bandeira et al., 2019).
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8 2. Material and methods
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2.1. Study area 168
Wild specimens were collected from 7 out of 9 provinces where the species is 169
distributed in mainland Portugal (Barros & Fonseca, 2011; Bandeira et al., 2018). The 170
Tagus River was considered a geographic barrier because it delimited the species’
171
historical distribution up to the 1990’s (Borralho et al., 1996; Barros & Fonseca, 2011).
172
This barrier divides two regions, north and south, considered different due to ecological, 173
climatic and human pressure factors (Bandeira et al., 2016, Bandeira et al., 2018;
174
Bandeira et al., 2019). The south is dominated by agroforestry habitats ("montados") 175
and shrubs, with higher temperatures and lower levels of rainfall (Hijmans et al., 2005;
176
Bandeira et al., 2016; Bandeira et al., 2018). In the north, human pressure is higher, 177
with more extensive road network and urbanized areas, greater habitat variability and 178
fragmentation (monoculture of Eucalyptus sp. overlapping with native flora such as 179
deciduous Quercus species, Salix sp. or Alnus glutinosa), more mountainous ridges and 180
a greater number of kilometers of hydrographic network (Alves et al., 2009; European 181
Commission, 2015; IGP, 2015; SNIRH, 2015; Bandeira et al., 2018). Specimens were 182
assigned to one of the two regions divided by the Tagus River according to their 183
location of capture (Figures 1 and 2).
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2.2. Sampling procedures 186
Carcasses of Egyptian mongoose were collected between January 2008 and December 187
2014 from hunting management activities (under legal game management actions aimed 188
9 at controlling predator densities) approved by national authorities (ICNF – Instituto da 189
Conservação da Natureza e das Florestas). The date of collection determined the season 190
assigned to each individual: winter for individuals collected between January and 191
March, spring (April to June), summer (July to September) and autumn (October to 192
December). Carcasses were labeled with the date and place of collection, and stored at - 193
20°C. In the laboratory, thawed carcasses were sexed, weighed, measured [snout-tail 194
length (terminal hairs not included), right hind leg length, right hind foot length, 195
shoulder height, neck perimeter, and head width] and dissected (Bandeira et al., 2016).
196
Lactating females were identified according to the development of the mammary glands 197
(milk present in mammary glands) and external nipples (Hoffmann et al., 1984; Abe et 198
al., 2006). Spleens and reproductive organs were collected and weighed separately to 199
the nearest 0.0001g scale. The male reproductive system was dissected, with both 200
testicles extracted from testicular sacs and separated from the epididymi (Soares &
201
Hoffmann, 1981; Soares & Hoffmann, 1982). Testes were weighed together and 202
measured in length and width with a caliper (Soares & Hoffmann, 1981; Soares &
203
Hoffmann, 1982). Ovaries were dissected from the female reproductive tract, weighed 204
together and measured (Hoffmann et al., 1984; Parsons et al., 2013). Only individuals 205
with intact skulls and reproductive systems were included in the study. Number of 206
embryos or fetuses in the developing female uterus was counted (the smallest embryo 207
detected had 0.8 cm in diameter) to calculate litter size (mean ± standard deviation) 208
(Hoffmann et al., 1984; Abe et al., 2006; Parsons et al., 2013). The age of each 209
specimen was determined by the analysis of dental development (Bandeira et al., 2016).
210
Each specimen was assigned to one of four age cohorts: adults over one year of age, 211
sub-adults between nine and twelve months, juveniles type II between five-and-a-half 212
and nine months, and juveniles type I between two-and-a-half and five-and-a-half 213
10 months of age according to Bandeira et al., (2016). We only used the reproductive 214
systems of 507 animals. All included specimens were box-trapped (traps were visited 215
twice daily), slaughtered with one or more shots to the head and had intact bodies and 216
spleens, and were the same animals used in the study published by Bandeira et al.
217
(2019). Therefore, we assume the effect of hemorrhage to be similar in all specimens, 218
and that spleen blood depletion would not confound the data for our intended purposes 219
by accounting mostly for splenic parenchima and not for splenic blood. We did not aim 220
to differentiate between the immune branches supported by the lymphoid and blood 221
filtering parts of the spleen (white and red pulp) but instead on the use of organ size 222
itself, as done previously for the spleen (e.g. Corbin et al., 2008, Bandeira et al., 2019) 223
and other organs with immune function like the thymus and bursa de Fabricius (see 224
Martin et al., 2008).
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2.3. Environmental Variables 227
For modeling, we selected five environmental variables based on the physiology and 228
ecology of Egyptian mongoose, that could somehow influence reproduction (e.g.
229
Bandeira et al., 2016, Bandeira et al., 2018; Bandeira et al., 2019). Considering the 230
critical home area of the Egyptian mongoose (Palomares & Delibes 1991b) each 231
specimen was assigned values of variables represented as mean values for the 2 x 2 km 232
grid where it was collected. These variables included the number of hectares allocated 233
to each habitat type (urban, rice fields, agro-forestry, shrubs, inland water bodies, 234
vineyards and orchards, coniferous, broadleaved and mix forests and agriculture areas) 235
with a spatial resolution of 250 m (Corine Land Cover, 2006) and converted into a 236
single categorical variable represented by the most abundant habitat type in each grid 237
11 cell. Human population density values are presented as the number of inhabitants per 238
square kilometer (data from Eurostat per kilometer) (European Commission, 2015).
239
Road and river network values refer to the length in meters of road (IGP, 2015) and 240
hydrographic network (SNIRH, 2015), respectively. Finally, a proxy of Egyptian 241
mongoose density (number of animals/400ha) was included based on the number of 242
animals captured in each area and in the month in which each sample was collected, 243
according to annual hunting bag (ICNF, unpublished data).
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2.4. Statistical procedures 246
The weight of the ovaries and testes was corrected for the total weight of each animal 247
and is presented as a standard value in milligrams per 100 g of animal total weight 248
(Soares & Hoffmann, 1981; Hoffmann et al., 1984). Similarly, the spleen weight is 249
presented as a standard value in grams per 100 g of total animal weight (Corbin et al., 250
2008; Bandeira et al., 2019). Body size was calculated by combining specimen weight 251
and the six biometric measurements into a single value through a principal component 252
analysis (PCA), using all variables with loadings > 0.70. Body condition was calculated 253
according to the Scaled Mass Index [predicted body mass (in grams) for an individual 254
standardized to linear body measurement] (Peig & Green, 2009; Peig & Green, 2010).
255
Residuals were inspected for deviations from normality by means of Q-Q plots. All 256
residuals were normal.
257
All explanatory variables were checked for collinearity using variance inflation factors 258
(VIF) and a cut-off value of 3.0 was used to drop collinear variables in a stepwise 259
fashion according to Zuur et al. (2009). Only variables that presented VIF ≤ 3.0 were 260
retained for model construction. Models explaining variation in ovarian and testes 261
12 weight included the discrete variables region, habitat, age and season and the 262
interactions season x region, season x age and region x age, as well as the continuous 263
variables Egyptian mongoose density, extent of the river network, adjusted spleen 264
weight and body condition, that were not excluded by VIF analysis. For mixed 265
modelling we used Gaussian distribution, identity link function with province as a 266
random factor to control for non-independence of samples from the same area.
267
Model selection was performed using Akaike Information Criterion (AICc) and we built 268
models separately for ovarian and testes weight. We used procedures outlined in Zuur et 269
al. (2009). In summary, there was a ranking of all possible models using AICc 270
(Burnham & Anderson, 2002), and only those with differences in the values of AICc 271
(ith model - minimum AICc value) lower than 2 were considered as explanatory. When 272
multiple models were selected, we used a multi-model averaging approach (Burnham &
273
Anderson 2002). The relative importance of the variables included in the final models 274
was also estimated.
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13 3. Results
285 286
Sampling yielded a total of 507 reproductive systems of Egyptian mongoose, 269 287
females and 238 males, from two regions (north and south of Tagus River) and distinct 288
ages (Figures 1 and 2, Table A1).
289
The sample contained 20 pregnant females captured between December and July 290
(Figure 3). Most females were found pregnant during April (n=8), followed by March 291
(n=5), May (n=3), June (n=2), July (n=1) and December (n=1) (Figure 3). Southern 292
females were found pregnant mainly in March and April, and those from the north in 293
April (Figure 3). Twenty litters were sampled from the pregnant females (Figure 4), 294
most of which had three embryos or fetuses (n=10). The mean litter size was 2.75 ± 295
0.79 (Figure 4). Litters from the northern region had 2.70 ± 0.67 (n=10) embryos or 296
fetuses, whereas those from the south had 2.8 ± 0.92 (n=10) (Figure 4). A single record 297
of a birth of four cubs in a box-trap of hunting activities was obtained, whose weights 298
ranged between 67g and 82g, with a mean of 75.75g. Cubs measured between 21.10 and 299
21.60 cm, with a mean of 21.35 cm of total length (snout-tail length). The sample 300
contained 10 lactating females, all for the period between March and August, except 301
April, during which there were no cases (Figure 5). Most females were found lactating 302
during July (n=4), followed by May and August (n=2 each), and finally, March and 303
June (n=1 each) (Figure 5).
304
Two variables of anthropogenic factors (population density and extent of road network) 305
and the variable body size were excluded from the initial set of predictors for adjusted 306
ovarian weight, as well as for adjusted testes weight model construction, to avoid 307
multicollinearity (Table A2 and A3).
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14 Ovarian weights of adults presented a variation throughout the year, demonstrating two 309
different periods, one with heavier ovaries from December to June (except January, 310
when lower values were registered), and a second period between July and November, 311
with lower ovarian weights (Figure 6). This variation was confirmed by measurements 312
of the lengths and widths of the ovaries, which increase or decrease in the same 313
proportion and in the same periods (Figure A1). After ranking all possible models using 314
AICc, two models (model 1: season; model 2: adjusted spleen weight + season) with 315
AICc < 2 were obtained (Tables A4 and A5). Season was the variable that presented 316
higher relative importance (Table 1). Females with heavier ovaries were found in 317
spring, followed by winter, summer and autumn (Table 1). Moreover, model analysis 318
reveals that females with heavier spleens also exhibited heavier ovaries (Table 1 and 319
Figure 7), revealing an association between reproductive and immunological systems.
320
Weight of adult testes showed a peak in February and remained rather constant 321
throughout the remainder of the year (Figures 8). After ranking all possible models 322
using AICc, two models (model 1: adjusted spleen weight + season + habitat + age + 323
region + season x age + season x region + age x region; model 2: adjusted spleen weight 324
+ season + habitat + age + region + Egyptian mongoose density + season x age + season 325
x region + age x region) with AICc < 2 were obtained (Tables A4 and A6). Adjusted 326
spleen weight, season, age, habitat and region were the variables that presented higher 327
relative importance, and season x age, season x region, and age x region were the 328
interactions (Table 2). Males found to the north of the Tagus River had heavier testes 329
than Southern males (Table 2). Adult males had heavier testes compared to other age 330
cohorts, increasing with age (Table 2). Testes were heavier during summer (Table 2).
331
Males with lighter spleens had heavier testes (Table 2). Males with heavier testes were 332
found in shrubs and in areas with higher density of conspecifics (Table 2). Regarding 333
15 the interaction between region and age, it was found that the southern adults presented 334
lighter testes (Table 2). The interaction between region and season showed that in 335
autumn, animals from south of the Tagus river had heavier testes (Table 2). The 336
interaction between age and season showed some seasonal variation between testicular 337
weight and the various age cohorts (Table 2).
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16 4. Discussion
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356
In carnivores, the reproductive cycle is regulated by photoperiod (Ruiz-Olmo, 1997) 357
wherein the beginning of reproductive activity in females is indicated by the increasing 358
mass of the ovaries (Carnaby et al., 2012). The results of this study confirm that the 359
Egyptian mongoose is a seasonally breeding species. First, females with heavier ovaries 360
were found in spring, followed by winter, summer and then autumn. This variation 361
reflected two clearly different periods in the species’ reproductive cycle, one of ovarian 362
activity between December and June (between the winter and late spring) and one of 363
inactivity from July to November. However, right after the initial rise in December, 364
lower ovarian weight is observed in January. As we are studying a large population, if 365
ovarian activity starts sooner in the southern areas than in the northern areas, we could 366
observe two different peaks when combining the data of the entire population 367
altogether. Hence, the first and second peaks in ovarian weight may be the result of 368
latitudinal variations in the beginning of ovulation, as is observed in a sympatric species 369
– the red fox (Vulpes vulpes) (Cavallini & Santini, 1995), or due to variables that were 370
not encompassed in our data.
371
Secondly, pregnant females were found in late winter, spring and early summer, 372
corresponding to the period where ovarian weight records were higher. This suggests 373
that in most cases Egyptian mongoose females produce only one litter per year, during 374
the same period as other sympatric carnivores (Ruiz-Olmo, 1997). To the south of the 375
Tagus River, pregnancies were most frequent in March and April, while to the north 376
pregnancies seem to be further distributed throughout spring. One of the females of the 377
northern region was found pregnant during December, and could represent either a 378
17 precocious breeding (since a peak in ovarian weight and size were observed in this 379
month) or the first litter from a late primiparous female (Ruiz-Olmo, 1997). Litter size 380
can range from one to four cubs, as in Israel (Ben-Yaacov & Yom-Tov, 1983), with 381
three as the modal value, and litters of the southern region were slightly larger. This 382
may reflect higher habitat quality in the southern region of the study area, where 383
mongooses reach higher densities and exhibit higher body condition (Bandeira et al., 384
2016; Bandeira et al., 2019). Finally, based on our results, the lactation period in 385
females occurs from late winter to the peak of summer. The absence of lactating 386
females from September forward indicates that at this time there are no longer cubs in 387
dens and that the offspring already accompany the mother in search of food, which 388
coincides with descriptions of larger groups, observed starting from July (Ben-Yaacov 389
& Yom-Tov, 1983; Palomares, 1993c; Palomares & Delibes, 1993a).
390
Herpestes ichneumon males did not show a marked reduction in testicular weight during 391
autumn, as opposed to the males of H. auropunctatus (from several islands of Hawaii) 392
that exhibit distinct active and inactive breeding periods (Soares & Hoffmann, 1981;
393
Soares & Hoffmann, 1982). The results of this study indicate that the Egyptian 394
mongoose males seem to be able to reproduce all year round (Palomares, 1993b), 395
despite a peak in testicular weight in February, which coincides with the period of 396
maximum ovarian weight in females. Together, these results suggest that the peak of the 397
breeding period of the Egyptian mongoose in Portugal begins in February. This pattern 398
coincides with the findings reported for this species in Spain (Palomares & Delibes, 399
1992) and in a closely related species, Herpestes auropunctatus (Hoffmann et al., 400
1984). Further, our results suggest that males do not have a well-defined breeding 401
season and that females are responsible for the timing of reproduction in this species, as 402
occurs with the majority of mammalian species.
403
18 The two models that best explained variation in ovarian weight in our sample contained 404
only two predictors: season and spleen weight. As expected for a photoperiod- 405
dependent breeder, season had the most influential effect. However, while the 406
reproduction-immunity trade-off hypothesis predicted that spleen weight would have a 407
negative association on ovarian weight in our models, we found the opposite. In fact, 408
the seasonal variation in ovarian weight parallels the variation in spleen weight, with 409
larger spleens found in spring, then in winter, summer and finally autumn (Bandeira et 410
al., 2019). While considering spleen weight is an indicator of immune function 411
(Fernández-Llario et al., 2004; Goüy de Bellocq et al., 2007), these results contradict a 412
reduction in immune capacity during the active reproductive period in Egyptian 413
mongoose females, and therefore a negative trade-off scenario (see Lochmiller &
414
Deerenberg, 2000; French et al., 2007). These findings are in agreement with growing 415
evidence of a complex regulation of immune function during pregnancy, in order to 416
simultaneously avoid an autoreactive response to the foetuses while maintaining the 417
ability to protect the female against pathogens (Muzzio et al., 2014). Recent studies in 418
mice have demonstrated complex changes to B cell function (Muzzio et al., 2014) and 419
increased cellularity, erythropoiesis and myelopoiesis in the spleen, regulated by 420
oestrogen (Nakada et al., 2014), thus explaining the increase in spleen size observed in 421
pregnancy in the species. The parallel variation of ovary and spleen weight in our study, 422
irrespective of variations in body condition scores, supports the hypothesis of a 423
simultaneous investment in reproductive and immune function in female Egyptian 424
mongoose.
425
The two models that best explained the variation in testicular weight included season 426
and spleen weight, but also several other predictors, specifically age, habitat, region, 427
mongoose density and interactions between season, region and age. While the effect of 428
19 age represents testicular development as young males grow, the effects of habitat type, 429
region and density of conspecifics (results based on hunting bag data should be 430
interpreted cautiously, since they are vulnerable to bias in capture effort) suggest that 431
male gonadal weight in this species shows a heavier influence from environmental 432
conditions, differing to what is observed in females. Also contrasting with females, 433
Egyptian mongoose males with lighter spleens had heavier testes, suggesting a trade-off 434
between reproduction and immunity (Zuk & Stoehr, 2002; Stoehr & Kokko, 2006).
435
Finally and most notably, the predictor body condition was absent in all models 436
explaining gonadal weight variation in this species. While in the model for females, the 437
absence of an immunity-reproduction trade-off and of an effect of body condition 438
together could in theory be explained by a situation where energy is simply not limited, 439
this explanation does not fit the case of males. In the case of Egyptian mongoose males, 440
there is a negative association of spleen weight on testicular weight, and the result is 441
supportive of a negative reproduction-immunity trade-off, regardless of body condition.
442
These results suggest that such a trade-off might not be mediated by simple energetic 443
allocation, but rather by other physiological pathways, either directly linking the 444
immune and reproductive systems, or simultaneously influencing them, such as 445
adrenocortical axis (see Manteuffel, 2002). Additionally, given that potential trade-offs 446
mediated by energy availability may only become evident when resources are scarce 447
and that Herpestes ichneumon breeds when food is maximally available (Bandeira et 448
al., 2018), such a trade-off may not be present (in females) or show an association with 449
body condition (in both sexes). Further studies focusing on alternative pathways are 450
necessary to understand how this inferred trade-off is mediated.
451
Overall, the results of this study refine our knowledge on Egyptian mongoose 452
reproductive ecology. They show that females are responsible for the timing of 453
20 reproduction, experiencing little influence from environmental conditions, while males 454
seem to be reproductively active year-round and are influenced by environmental 455
variables. Additionally, our results demonstrate a sex-biased association between 456
reproduction and immunity in Herpestes ichneumon that is unaffected by body 457
condition, suggesting a reproduction-immunity trade-off in males, but not in females 458
where reproductive and immune organ mass are positively correlated.
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21 Author Contributions
475
VB, EV and CF conceived and designed the field and laboratory work. VB and AA 476
performed the field and laboratory work. VB and EV analyzed the data and performed 477
statistical analyses. VB, EV, AA, MVC and CF wrote the manuscript. All authors 478
contributed to the development of ideas and approved the final version of the 479
manuscript.
480
481
Conflict of interest 482
Authors declare no conflict of interest.
483
484
Acknowledgments 485
486
Thanks to collectors, hunters, entities managing hunting areas and their representatives, 487
namely FENCAÇA, ANPC and CNCP, to Tapada Nacional de Mafra and to all that 488
contributed to the sampling. To Carlos Pimenta (DGPC- Laboratório de 489
Arqueociências, SEC – Direção Geral do Património Cultural) for providing the method 490
for the enzymatic cleaning of skulls. We would like to thank Dr. Madalena Monteiro, 491
Dr. Paulo Carvalho and Dr. Paula Mendonça, veterinarians of Instituto Nacional de 492
Investigação Agrária e Veterinária, I.P. in Lisbon (INIAV) for some of the samples 493
harvest. To João Carvalho for the sampling map locations and for bioclimatic data. To 494
National Funds through FCT and European funds through the COMPETE and FEDER 495
by co-funding through the project "Genetic assessment of a successful invasion:
496
Population genetics of the Egyptian mongoose (Herpestes ichneumon) in Portugal", 497
22 PTDC/BIA-BEC/104401/2008. We would like to thank FCT/MCTES for the financial 498
support to CESAM (UIDP/50017/2020+UIDB/50017/2020) through national funds. To 499
Doctoral Program in Biology and Ecology of Global Change of University of Aveiro 500
and University of Lisbon. Victor Bandeira was supported by FCT doctoral grants 501
(SFRH/BD/ 51540/2011). We thank two anonymous reviewers for their helpful 502
comments.
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
23 References
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31 Tables
691
692
Table 1. Model-averaged coefficients for the effects of explanatory variables on ovarian 693
weight of the Egyptian mongoose in Portugal.
694
Variables Estimate Std.
Error Z value Relative importance
Intercept 2.358 0.178 13.279
SEASON Autumn -0.340 0.197 1.726 1.00
Spring 0.368 0.191 1.927
Summer -0.253 0.192 1.321
ADJUSTED SPLEEN WEIGHT 0.118 0.436 0.270 0.28
695 696 697 698 699 700 701 702 703 704 705
32 Table 2. Model-averaged coefficients for the effects of explanatory variables on testes 706
weight of the Egyptian mongoose in Portugal.
707
Variables Estimate Std. Error z value Relative
importance
Intercept 130.096 13.772 9.446
SPLEEN WEIGHT -8.001 9.757 0.820 1.00
SEASON Autumn -2.741 15.427 0.178 1.00
Spring -11.459 13.596 0.843
Summer 7.869 15.951 0.493
AGE Juvenile 1 -107.576 32.483 3.312 1.00
Juvenile 2 -57.399 22.004 2.609
Sub-adult -37.482 13.868 2.703
HABITAT Agro-forestry 0.470 6.611 0.071 1.00
Broadleaved and mixed forests
7.602 5.467 1.390
Rice fields 7.516 30.789 0.244
Shrubs 9.186 10.343 0.888
Urban 8.664 12.632 0.686
Vineyards and orchards -7.851 21.568 0.364
REGION South -24.701 13.009 1.899 1.00
EGYPTIAN MONGOOSE DENSITY 0.152 1.031 0.147 0.40
REGION x AGE South x Juvenile1 24.070 14.565 1.653 1.00 South x Juvenile2 21.660 13.266 1.633
South x Sub-adult 5.187 13.484 0.385
REGION x SEASON South x Autumn 1.971 15.346 0.128 1.00 South x Spring -8.712 14.537 0.599
South x Summer -21.303 17.727 1.202
33 AGE x SEASON Juvenile1 x Autumn -2.994 33.342 0.090 1.00
Juvenile1 x Spring 20.994 31.809 0.660 Juvenile1 x Summer 6.623 31.144 0.213 Juvenile2 x Autumn -31.724 20.391 1.556 Juvenile2 x Spring -17.928 20.349 0.881 Juvenile 2 x Summer -31.554 20.044 1.574 Sub-adult x Autumn -35.675 13.892 2.568 Sub-adult x Spring -6.493 19.099 0.340 Sub-adult x Summer -28.408 31.733 0.895 708
709 710 711 712 713 714 715 716 717 718 719 720 721 722
34 Figure legends
723
724
Figure 1. Locations and number of samples of the female Egyptian mongoose 725
specimens under study.
726
Figure 2. Locations and number of samples of the male Egyptian mongoose specimens 727
under study.
728
Figure 3. Number of pregnant females of the Egyptian mongoose among regions by 729
month (n=20).
730
Figure 4. Number of litters with n embryos of the Egyptian mongoose among regions 731
(n=20).
732
Figure 5. Number of lactating females of the Egyptian mongoose by month (n=10).
733
Figure 6. Ovarian weight (expressed as mg/100g of total body weight) of 157 adult 734
females of the Egyptian mongoose over month. (n) is the number of females in each 735
month. Vertical lines represent the standard error of the mean.
736
Figure 7. Scatterplot of 269 Egyptian mongoose ovarian weight (expressed as mg/100g 737
of total body weight) observed for spleen weight (expressed as g/100g body weight).
738
Dashed lines denote 95% confidence intervals. Ovarian weight = 2.1555+0.4241x 739
Figure 8. Testes weight (expressed as mg/100g of total body weight) of 116 adult males 740
of the Egyptian mongoose over month. (n) is the number of males in each month.
741
Vertical lines represent the standard error of the mean.
742
743
35 Appendix
744
745
Table A1. Numbers of Egyptian mongoose samples obtained for each region, north and 746
south of the Tagus River, together with information on age cohort and sex.
747
Age Sex Region
North South
Adult Female 47 110
Male 35 81
Sub-adult Female 12 31
Male 16 22
Juvenile II Female 5 31
Male 9 46
Juvenile I Female 4 29
Male 9 20
Total Female 68 201
Male 69 169
748 749 750 751 752 753
