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A Preliminary Report on the Seasonal Changes of the Hair-color of the Harvest Mice and its Taxonomical Importance

B y J . SZUNYOGHY, Budapest

Since P a l l a s described Micromys minutus in 1771, 23 species and subspecies from Europe and 10 from Asia of the harvest mice were made known up to now. I n this jungle of species and subspecies M i l l e r was the first to t ry and introduce some order, who, in his cata­logue of mammals published in 1912, recognized, with the exception of the harvest mice of Russia, but two subspecies, the western Micromys minutus soricinus, and the Central European Micromys minutus pratensis. M i l l e r regarded, for instance, 18 harvest mice species and subspecies as identical, that is, synonymous with Micromys minutus soricinus. This extensive synonymization was the best witness to show that there is something amiss in the systematics of the harvest mice. M i l l e r himself commented on this, when he wrote, in his catalogue of mammals, as follows : ,,For the present i t seems neccessary to regard all the harvest mice of western Europe, including England and northern Italy, as belonging to a single race. The differences which have been observed to exist, notably between British and German specimens, prove to be merely seasonal" (p. 845). M i l l e r ' s comment is interesting also from the point of view that he took note of the seasonal change of the pelage.

E l l e r m a n n & M o r r i s o n — S c o t t recognized from Europe, in their work published in 1951, 7 harvest mice subspecies, as follows : 1. Micromys minutus minutus Pallas 1771. 2. M. M. soricinus Hermann 1780. 3. M. m. pratensis Oeskay 1831. 4. M. m. fenniae Hilzheimer 1911. 5. M. m. méhelyi Bolkay 1925. 6. M. m. brauneri Martino 1930, 7. M. m. subobscurus Fritsche 1934.

Of the above 7 subspecies, the description of four (M. m. soricinus, praten­sis, fenniae, subobscurus) was based almost exclusively on the coloration of the hairs, playing an important role also in the case of two further ones (M. m. minutus, M. m. brauneri). Only in the case of one subspecies, M. m. méhelyi, did the author disregard coloration.

As is to be seen from the aboves, the coloration of the pelage has an important role i n the taxonomical segregation of the harvest mice.

By the assiduous work of several years, I was successful to collect 231 specimens (172 skulls and skins, and 59 skulls only) of the home harvest mice, known in literature as Micromys minutus pratensis. I n this material, there are specimens of various age and from several seasons.

After having sorted out this material according to seasons, and wi th in them to months, I found that the coloration of the pelage changes seasonally. Taken i n itself, this is not very striking, since the summer pelage of most of our mammals is lighter, and the winter ones greyer, duller, darker. My studies were interesting however from the point of view that, as far as I know i t , nobody

has as yet thoroughly studied the seasonal changes of the hair-color of the harvest mice.

On the basis of my Hungarian harvest mice material, one could first of all establish the typical summer coloration. I n this regard, the upperpart of the body is almost uniformly reddish brown, to be designated also as rusty brown, yellow-reddish brown, or fox-red. The underpart is mostly snow white.

The upperpart of the body is „a lmost uniformly" reddish brown inasmuch only as one may observe some differences i n tinge. Namely, the reddish brown color is the most intensive, that is, the lightest, around the line of contact of the upper and lower parts of the body, notably on the head, the legs, the sides of the body and around the ta i l . This lighter color darkens towards the dorsal area. This transition from the lighter sides of the body into the darker color­ation of the dorsal area is but gradual and does not mean the bicoloration of the upperpart, only a fine difference i n t i n t . The hairs of the dorsal side are bicoloured. Their base, for about two-third of the length of the hair, is a lighter or darker ashen grey, whilst their t ip , for about one-third of their length, is yellowish red. Dispersed among these hairs, there are hairs longer than the above ones, l ight greyish i n their lower part and dark brownish bluishgrey in their upper part. The coloration of the upperpart (in which there is therefore but a difference in t in t ) may, obviously, be lighter or darker, but always more v iv id and lighter than the typical winter coloration.

And the underpart of the body is ,,mostly snow whi te" inasmuch as, i n the majority of the cases, i t is really such, yet one may f ind, i n a small per­centage, pelages of a reddish or yellowish t i n t (flavistical specimens?). The underpart are covered therefore by hairs snow-white down to their bases or, more seldom, by yellowish-reddish hairs i n the summer. The base of the hairs is, however, never grey.

Towards the end of summer, i n the fall , the modification of the color of the pelage begins. A certain proportion of the animals, namely generally the biggest and therefore the oldest specimens (though there are exceptions), may yet retain their typical summer pelage, but the majority of them begins to alter. This modification i n color extends from the head towards the caudal region, but w i l l never reach i t wholly. A t this time, the head, neck, shoulders and back loose their summertime yellowish or reddish brown color, and become greyish brown. On the other hand, the lighter reddish brown color s t i l l persists around the caudal, that is, the pelvic regions. I n this way, the pelage on the dorsal area of the harvest mice becomes bicoloured already i n early autumn. This greying may be observed also i n the connecting line between the upper and underparts, yet the color is st i l l lighter and more v iv id .

B y the greying of a portion of the upperpart, the summertime snow white coloration of the underpart w i l l correlatively become greyer. The graying refers either to the whole length of the hairs or but to their bases. This gradual greying may explain the fact that several authors refer to a greyish, ashen grey, silver grey, or whitish coloration on the underpart.

Approaching winter, one may f ind that the number of specimens w i t h the summer coloration decreases, concomitantly w i t h the increase of speci­mens of greyish upper and underparts.

The expressedly wintertime coloration differs only inasmuch from the autumnal one that the greying increases on the upper and underparts.

W i t h the passing away of the winter months, the lightening of the

coloration of the pelage commences, reaching its maximum during the summer months.

The transition from the summer into the winter coloration seems to be gradual. The most heterogenous, and so seemingly the most inscrutable, are the spring and fall colorations, when, beside the summer ones, also the autumnal, sometimes the winter, that is, expressedly winter and spring colorations also appear.

As an explanation to my descriptions, I have grouped according to months the Micromys material of the Hungarian and Berlin Natural History Museums

in the enclosed figure. The segregation of the typically summer and winter pelages i n the summer and winter months is well discernible, whilst the color distribution i n the transitional fall and spring months is not so uniform.

This change in coloration discussed above is surely depending on the pre­vailing weather, aside of individual features. I n the case of a cold fall and an early winter therefore, the winter coloration may appear earlier, and given a long winter, cold spring and early summer, the summer coloration may turn up later.

Having established this color modification for the Hungarian harvest mice (Micromys minutus pratensis), I endeavoured to receive comparative material from abroad. So, I succeeded to receive as a loan, from the terr i tory of Germany, 32 harvest mice specimens (18 skins -f- skulls, 14 skulls) from professor H . K a h m a n n (Munich), and 159 skins and 98 skulls from pro­fessor K . Z i m m e r m a n n . I t is my agreebly duty to express my thanks

for their k ind cooperation also i n this place. The German material was most valuable for me not only because i t contained M. m. soricinus and M. m. subob-scurus subspecies, but because i t well completed my Hungarian material w i t h regard to the dates of collectings. The German harvest mice material originates, namely, mostly from the winter months, whilst the Hungarian one from the summer and fall months.

On the basis of the comparative materials received, i t could be established that the seasonal changes i n coloration also refer to the German specimens.

But i t could also be established that there is no essential difference i n coloration between the Hungarian and German harvest mice. I t follows there­fore that , instead of M. m. pratensis, there lives in Hungary M. m. soricinus.

Besides, i t became plain that M. m. subobscurus is nothing else but the seasonal, winter-colored form of M. m. soricinus.

Furthermore, one ought to revide all those harvest mice subspecies of Europe i n the description of which the coloration of the hairs plays an important role, lest the seasonal forms of a subspecies be registered as distinct subspecies also i n the future.

One thing is certain, and that is that the synonymizing of the subspecies of the harvest mice began by M i l l e r should be continued, finding those anatomical or morphological features by which the segregation of the Micromys subspecies can safely be carried through. The coloration of the pelage does not seem adequate for this purpose. I wish to detailedly discuss all these problems i n a paper of mine soon to be published.

T H E S E A S O N A L C H A N G E S O F T H E H A I R - C O L O R O F T H E H A R V E S T M I C E . 347

Предварительное сообщение о сезонном изменении масти мышей-малюток и о систематологическом значении зтого

явлении

Я. Суньоги, Будапешт

(РЕЗЮМЕ) Э л л е р м а н и и М о р р и с о н— С к о т т в своей опубликованной в

1951 году работе определили в Европе 7 подвидов мышей-малюток. Из этих под­видов описание четырех(М. т. зоггсгпиз, рга1епзг8, {ептае, зиооЬзсигиз) произошло почти исключительно на основании масти, а у двух подвидов (М. т. тгпиШз, М. т. Ъгаипеп) масть играет важную роль. Лишь в случае одного подвида (М. т. тёНе1у1) автор не принимал во внимание масти. Следовательно, при систематологическом определении мышей-малюток масть играет важную роль.

На основании венгерского материала мышей-малюток было установлено, что масть проявляет сезонные изменения. Летом верхняя поверхность тела почти равномерно краснобурая, а нижняя часть тела в большинстве случаев снежно-белая. К концу лета, осенью, начинается изменение цвета волосяного покрова. Голова, шея, плечо и спина утрачивают летний светло желтый, или красно-бурый цвет и становятся сероватобурыми, значит, они посереют. В противопо­ложность этому около ягодицы светлая краснобурая часть остается. На линии соприкосновения спины и брюшной стороны также наблюдается посерение, хотя масть на этом месте остается всегда более светлой. Таким образом мех мышей-малюток на спинной стороне уже ранней осенью становится двуцвет­ным. При посерении одной части спинной стороны, летняя белоснежная масть брюшной стороны также постепенно становится серой.

Зимняя масть различается от осенней масти только в том, что посерение на спинной и брюшной сторонах повышается. После зимних месяцев масть начинает светлеть и достигает максимума посветления летом.

Переход от летней масти к зимней и наоборот кажется постепенным. Больше всего смешанной и следовательно меньше всего определяемой кажется осенняя и весенняя масти, когда наряду с выражение летней мастью иногда встре­чается и осенняя и зимняя, или наряду с выраженной зимней мастью текже и весенняя и летняя масти.

Изменения цвета волосяного покрова автор показывает на рисунке, на котором он составил материал мышей-малюток венгерского и германского музеев естествоведения в группировке по отдельным месяцам.

На этом рисунке видно, что сезонное изменение масти действительно и для материала мышей-малюток в Германии.

Ввиду того, что между венгерскими и германскими мышами-малютками не наблюдалось значительной разницы, то следует на основании закона прио­ритета установить, что в Венгрии не живут М. т. рга1еп$18, а М. т. зоггсгпиз.

М. т. зиЬоЬзсигиз не является иным, как сезонной формой М. т. зогшпиз зимней масти.

Однако, сверх этого следовало бы пересмотреть все европейские подвиды мышей-малюток, при описании которых масть играет важную роль, чтобы специальная наука не учитывала в дальнейшем сезонных форм одного и того же подвида, как особый подвид. Автор в своей опубликуемой в ближайшем будущем статье подробно займется этими вопросами.